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	$222.76	5.478%	$234.9628	$234.96	$234.95	$235.00
Purchase #2	$243.92	4.870%	$255.7989	$255.80	$255.80	$255.80
Purchase #3	$222.29	12.565%	$250.2207	$250.22	$250.20	$250.20
Purchase #4	$222.80	11.789%	$249.0659	$249.07	$249.05	$249.10
Purchase #5	$49.70	11.586%	$55.4582	$55.46	$55.45	$55.50
Purchase #6	$59.87	7.353%	$64.2722	$64.27	$64.25	$64.30
Purchase #7	$238.77	11.219%	$265.5576	$265.56	$265.55	$265.60
7 purchase totals =	$1,260.11		$1,375.3363	$1,375.34	$1,375.25	$1,375.50