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	$100.60	10.159%	$110.82	$110.82	$110.80	$110.80
Purchase #2	$191.90	12.374%	$215.6457	$215.65	$215.65	$215.60
Purchase #3	$160.35	11.820%	$179.3034	$179.30	$179.30	$179.30
Purchase #4	$248.80	4.162%	$259.1551	$259.16	$259.15	$259.20
Purchase #5	$102.46	10.799%	$113.5247	$113.52	$113.50	$113.50
Purchase #6	$198.49	13.677%	$225.6375	$225.64	$225.65	$225.60
Purchase #7	$194.34	7.307%	$208.5404	$208.54	$208.55	$208.50
7 purchase totals =	$1,196.94		$1,312.6268	$1,312.63	$1,312.60	$1,312.50