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	$181.98	13.129%	$205.8722	$205.87	$205.85	$205.90
Purchase #2	$209.40	11.418%	$233.3093	$233.31	$233.30	$233.30
Purchase #3	$93.53	3.374%	$96.6857	$96.69	$96.70	$96.70
Purchase #4	$64.58	10.436%	$71.3196	$71.32	$71.30	$71.30
Purchase #5	$219.37	4.507%	$229.257	$229.26	$229.25	$229.30
Purchase #6	$145.60	4.754%	$152.5218	$152.52	$152.50	$152.50
Purchase #7	$247.87	6.809%	$264.7475	$264.75	$264.75	$264.70
7 purchase totals =	$1,162.33		$1,253.7131	$1,253.72	$1,253.65	$1,253.70