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	$155.61	10.459%	$171.8852	$171.89	$171.90	$171.90
Purchase #2	$215.98	12.397%	$242.755	$242.76	$242.75	$242.80
Purchase #3	$38.54	6.543%	$41.0617	$41.06	$41.05	$41.10
Purchase #4	$60.65	7.747%	$65.3486	$65.35	$65.35	$65.30
Purchase #5	$149.94	11.685%	$167.4605	$167.46	$167.45	$167.50
Purchase #6	$97.38	13.345%	$110.3754	$110.38	$110.40	$110.40
Purchase #7	$226.80	6.801%	$242.2247	$242.22	$242.20	$242.20
7 purchase totals =	$944.90		$1,041.1111	$1,041.12	$1,041.10	$1,041.20