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	$238.86	13.771%	$271.7534	$271.75	$271.75	$271.80
Purchase #2	$64.98	4.515%	$67.9138	$67.91	$67.90	$67.90
Purchase #3	$116.27	9.845%	$127.7168	$127.72	$127.70	$127.70
Purchase #4	$162.34	9.624%	$177.9636	$177.96	$177.95	$178.00
Purchase #5	$103.26	13.690%	$117.3963	$117.40	$117.40	$117.40
Purchase #6	$168.98	11.568%	$188.5276	$188.53	$188.55	$188.50
Purchase #7	$198.65	11.400%	$221.2961	$221.30	$221.30	$221.30
7 purchase totals =	$1,053.34		$1,172.5676	$1,172.57	$1,172.55	$1,172.60