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	$93.61	6.106%	$99.3258	$99.33	$99.35	$99.30
Purchase #2	$160.82	12.672%	$181.1991	$181.20	$181.20	$181.20
Purchase #3	$209.58	7.299%	$224.8772	$224.88	$224.90	$224.90
Purchase #4	$145.51	9.782%	$159.7438	$159.74	$159.75	$159.70
Purchase #5	$51.38	8.112%	$55.5479	$55.55	$55.55	$55.50
Purchase #6	$199.50	13.396%	$226.225	$226.23	$226.25	$226.20
Purchase #7	$223.86	11.401%	$249.3823	$249.38	$249.40	$249.40
7 purchase totals =	$1,084.26		$1,196.3011	$1,196.31	$1,196.40	$1,196.20