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	$124.31	13.478%	$141.0645	$141.06	$141.05	$141.10
Purchase #2	$198.68	10.300%	$219.144	$219.14	$219.15	$219.10
Purchase #3	$68.30	12.326%	$76.7187	$76.72	$76.70	$76.70
Purchase #4	$244.50	5.238%	$257.3069	$257.31	$257.30	$257.30
Purchase #5	$94.73	3.848%	$98.3752	$98.38	$98.40	$98.40
Purchase #6	$30.45	8.389%	$33.0045	$33.00	$33.00	$33.00
Purchase #7	$109.45	12.865%	$123.5307	$123.53	$123.55	$123.50
7 purchase totals =	$870.42		$949.1445	$949.14	$949.15	$949.10