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	$85.58	12.343%	$96.1431	$96.14	$96.15	$96.10
Purchase #2	$53.63	5.376%	$56.5131	$56.51	$56.50	$56.50
Purchase #3	$184.35	3.194%	$190.2381	$190.24	$190.25	$190.20
Purchase #4	$39.80	4.815%	$41.7164	$41.72	$41.70	$41.70
Purchase #5	$135.98	12.280%	$152.6783	$152.68	$152.70	$152.70
Purchase #6	$63.87	11.837%	$71.4303	$71.43	$71.45	$71.40
Purchase #7	$123.79	6.862%	$132.2845	$132.28	$132.30	$132.30
7 purchase totals =	$687.00		$741.0038	$741.00	$741.05	$740.90