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	$157.27	11.168%	$174.8339	$174.83	$174.85	$174.80
Purchase #2	$149.81	6.500%	$159.5477	$159.55	$159.55	$159.50
Purchase #3	$96.59	7.701%	$104.0284	$104.03	$104.05	$104.00
Purchase #4	$12.64	5.166%	$13.293	$13.29	$13.30	$13.30
Purchase #5	$81.59	4.573%	$85.3211	$85.32	$85.30	$85.30
Purchase #6	$89.99	5.704%	$95.123	$95.12	$95.10	$95.10
Purchase #7	$215.54	13.304%	$244.2154	$244.22	$244.20	$244.20
7 purchase totals =	$803.43		$876.3625	$876.36	$876.35	$876.20