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	$148.94	10.424%	$164.4655	$164.47	$164.45	$164.50
Purchase #2	$48.58	9.755%	$53.319	$53.32	$53.30	$53.30
Purchase #3	$70.73	10.530%	$78.1779	$78.18	$78.20	$78.20
Purchase #4	$155.61	8.745%	$169.2181	$169.22	$169.20	$169.20
Purchase #5	$132.48	3.283%	$136.8293	$136.83	$136.85	$136.80
Purchase #6	$199.30	12.366%	$223.9454	$223.95	$223.95	$223.90
Purchase #7	$247.66	7.112%	$265.2736	$265.27	$265.25	$265.30
7 purchase totals =	$1,003.30		$1,091.2288	$1,091.24	$1,091.20	$1,091.20