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	$10.47	7.677%	$11.2738	$11.27	$11.25	$11.30
Purchase #2	$222.96	12.323%	$250.4354	$250.44	$250.45	$250.40
Purchase #3	$199.28	13.345%	$225.8739	$225.87	$225.85	$225.90
Purchase #4	$162.72	11.445%	$181.3433	$181.34	$181.35	$181.30
Purchase #5	$34.52	10.252%	$38.059	$38.06	$38.05	$38.10
Purchase #6	$54.53	7.400%	$58.5652	$58.57	$58.55	$58.60
Purchase #7	$85.31	8.299%	$92.3899	$92.39	$92.40	$92.40
7 purchase totals =	$769.79		$857.9405	$857.94	$857.90	$858.00