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	$223.33	4.384%	$233.1208	$233.12	$233.10	$233.10
Purchase #2	$141.96	6.426%	$151.0823	$151.08	$151.10	$151.10
Purchase #3	$117.56	10.181%	$129.5288	$129.53	$129.55	$129.50
Purchase #4	$161.88	12.332%	$181.843	$181.84	$181.85	$181.80
Purchase #5	$135.68	4.404%	$141.6553	$141.66	$141.65	$141.70
Purchase #6	$74.88	4.791%	$78.4675	$78.47	$78.45	$78.50
Purchase #7	$245.77	9.526%	$269.1821	$269.18	$269.20	$269.20
7 purchase totals =	$1,101.06		$1,184.8798	$1,184.88	$1,184.90	$1,184.90