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	$185.86	10.363%	$205.1207	$205.12	$205.10	$205.10
Purchase #2	$216.68	11.821%	$242.2937	$242.29	$242.30	$242.30
Purchase #3	$220.85	9.347%	$241.4928	$241.49	$241.50	$241.50
Purchase #4	$203.97	6.632%	$217.4973	$217.50	$217.50	$217.50
Purchase #5	$80.64	12.663%	$90.8514	$90.85	$90.85	$90.90
Purchase #6	$226.35	10.178%	$249.3879	$249.39	$249.40	$249.40
Purchase #7	$145.78	13.218%	$165.0492	$165.05	$165.05	$165.00
7 purchase totals =	$1,280.13		$1,411.6930	$1,411.69	$1,411.70	$1,411.70