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	$145.40	10.850%	$161.1759	$161.18	$161.20	$161.20
Purchase #2	$196.37	11.657%	$219.2609	$219.26	$219.25	$219.30
Purchase #3	$28.81	13.396%	$32.6694	$32.67	$32.65	$32.70
Purchase #4	$165.85	8.470%	$179.8975	$179.90	$179.90	$179.90
Purchase #5	$74.75	5.420%	$78.8015	$78.80	$78.80	$78.80
Purchase #6	$236.84	5.171%	$249.087	$249.09	$249.10	$249.10
Purchase #7	$86.57	5.548%	$91.3729	$91.37	$91.35	$91.40
7 purchase totals =	$934.59		$1,012.2651	$1,012.27	$1,012.25	$1,012.40