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	$58.46	4.504%	$61.093	$61.09	$61.10	$61.10
Purchase #2	$240.27	3.375%	$248.3791	$248.38	$248.40	$248.40
Purchase #3	$114.94	12.132%	$128.8845	$128.88	$128.90	$128.90
Purchase #4	$233.41	13.713%	$265.4175	$265.42	$265.40	$265.40
Purchase #5	$143.71	4.124%	$149.6366	$149.64	$149.65	$149.60
Purchase #6	$170.35	11.850%	$190.5365	$190.54	$190.55	$190.50
Purchase #7	$24.30	13.433%	$27.5642	$27.56	$27.55	$27.60
7 purchase totals =	$985.44		$1,071.5114	$1,071.51	$1,071.55	$1,071.50