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	$56.89	7.794%	$61.324	$61.32	$61.30	$61.30
Purchase #2	$8.59	13.692%	$9.7661	$9.77	$9.75	$9.80
Purchase #3	$74.74	11.381%	$83.2462	$83.25	$83.25	$83.20
Purchase #4	$62.31	7.805%	$67.1733	$67.17	$67.15	$67.20
Purchase #5	$124.46	6.793%	$132.9146	$132.91	$132.90	$132.90
Purchase #6	$81.34	9.837%	$89.3414	$89.34	$89.35	$89.30
Purchase #7	$200.52	9.397%	$219.3629	$219.36	$219.35	$219.40
7 purchase totals =	$608.85		$663.1285	$663.12	$663.05	$663.10