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	$93.78	7.433%	$100.7507	$100.75	$100.75	$100.80
Purchase #2	$179.98	4.521%	$188.1169	$188.12	$188.10	$188.10
Purchase #3	$244.73	3.869%	$254.1986	$254.20	$254.20	$254.20
Purchase #4	$125.36	5.154%	$131.8211	$131.82	$131.80	$131.80
Purchase #5	$108.55	10.143%	$119.5602	$119.56	$119.55	$119.60
Purchase #6	$181.49	7.236%	$194.6226	$194.62	$194.60	$194.60
Purchase #7	$156.98	5.674%	$165.887	$165.89	$165.90	$165.90
7 purchase totals =	$1,090.87		$1,154.9571	$1,154.96	$1,154.90	$1,155.00