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	$100.36	10.637%	$111.0353	$111.04	$111.05	$111.00
Purchase #2	$216.58	5.317%	$228.0956	$228.10	$228.10	$228.10
Purchase #3	$61.47	9.410%	$67.2543	$67.25	$67.25	$67.30
Purchase #4	$51.47	5.852%	$54.482	$54.48	$54.50	$54.50
Purchase #5	$161.56	12.414%	$181.6161	$181.62	$181.60	$181.60
Purchase #6	$219.61	10.816%	$243.363	$243.36	$243.35	$243.40
Purchase #7	$193.66	7.785%	$208.7364	$208.74	$208.75	$208.70
7 purchase totals =	$1,004.71		$1,094.5827	$1,094.59	$1,094.60	$1,094.60