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	$51.25	4.375%	$53.4922	$53.49	$53.50	$53.50
Purchase #2	$223.69	10.518%	$247.2177	$247.22	$247.20	$247.20
Purchase #3	$36.63	3.823%	$38.0304	$38.03	$38.05	$38.00
Purchase #4	$95.84	9.661%	$105.0991	$105.10	$105.10	$105.10
Purchase #5	$213.84	7.139%	$229.106	$229.11	$229.10	$229.10
Purchase #6	$152.46	12.342%	$171.2766	$171.28	$171.30	$171.30
Purchase #7	$232.90	6.579%	$248.2225	$248.22	$248.20	$248.20
7 purchase totals =	$1,006.61		$1,092.4445	$1,092.45	$1,092.45	$1,092.40