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	$31.27	3.335%	$32.3129	$32.31	$32.30	$32.30
Purchase #2	$129.47	12.494%	$145.646	$145.65	$145.65	$145.60
Purchase #3	$67.46	5.751%	$71.3396	$71.34	$71.35	$71.30
Purchase #4	$148.41	13.177%	$167.966	$167.97	$167.95	$168.00
Purchase #5	$231.57	12.217%	$259.8609	$259.86	$259.85	$259.90
Purchase #6	$119.52	12.802%	$134.821	$134.82	$134.80	$134.80
Purchase #7	$242.85	4.677%	$254.2081	$254.21	$254.20	$254.20
7 purchase totals =	$970.55		$1,066.1545	$1,066.16	$1,066.10	$1,066.10