Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$191.46	10.449%	$211.4657	$211.47	$211.45	$211.50
Purchase #2	$153.68	11.346%	$171.1165	$171.12	$171.10	$171.10
Purchase #3	$82.28	10.821%	$91.1835	$91.18	$91.20	$91.20
Purchase #4	$226.79	13.787%	$258.0575	$258.06	$258.05	$258.10
Purchase #5	$140.68	4.686%	$147.2723	$147.27	$147.25	$147.30
Purchase #6	$149.54	10.669%	$165.4944	$165.49	$165.50	$165.50
Purchase #7	$127.81	4.414%	$133.4515	$133.45	$133.45	$133.50
7 purchase totals =	$1,072.24		$1,178.0414	$1,178.04	$1,178.00	$1,178.20