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	$174.29	12.825%	$196.6427	$196.64	$196.65	$196.60
Purchase #2	$64.67	10.128%	$71.2198	$71.22	$71.20	$71.20
Purchase #3	$108.93	7.305%	$116.8873	$116.89	$116.90	$116.90
Purchase #4	$66.91	7.331%	$71.8152	$71.82	$71.80	$71.80
Purchase #5	$96.73	5.246%	$101.8045	$101.80	$101.80	$101.80
Purchase #6	$45.44	10.680%	$50.293	$50.29	$50.30	$50.30
Purchase #7	$92.55	7.167%	$99.1831	$99.18	$99.20	$99.20
7 purchase totals =	$649.52		$707.8456	$707.84	$707.85	$707.80