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	$137.33	10.675%	$151.99	$151.99	$152.00	$152.00
Purchase #2	$104.32	6.695%	$111.3042	$111.30	$111.30	$111.30
Purchase #3	$63.52	5.690%	$67.1343	$67.13	$67.15	$67.10
Purchase #4	$172.48	7.431%	$185.297	$185.30	$185.30	$185.30
Purchase #5	$43.89	6.522%	$46.7525	$46.75	$46.75	$46.80
Purchase #6	$198.91	6.481%	$211.8014	$211.80	$211.80	$211.80
Purchase #7	$135.70	12.629%	$152.8376	$152.84	$152.85	$152.80
7 purchase totals =	$856.15		$927.1170	$927.11	$927.15	$927.10