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	$145.96	4.582%	$152.6479	$152.65	$152.65	$152.60
Purchase #2	$211.93	7.538%	$227.9053	$227.91	$227.90	$227.90
Purchase #3	$91.58	8.261%	$99.1454	$99.15	$99.15	$99.10
Purchase #4	$218.43	9.449%	$239.0695	$239.07	$239.05	$239.10
Purchase #5	$114.38	11.646%	$127.7007	$127.70	$127.70	$127.70
Purchase #6	$56.41	10.754%	$62.4763	$62.48	$62.50	$62.50
Purchase #7	$133.52	8.443%	$144.7931	$144.79	$144.80	$144.80
7 purchase totals =	$972.21		$1,053.7382	$1,053.75	$1,053.75	$1,053.70