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	$157.69	3.287%	$162.8733	$162.87	$162.85	$162.90
Purchase #2	$110.73	7.298%	$118.8111	$118.81	$118.80	$118.80
Purchase #3	$234.71	8.771%	$255.2964	$255.30	$255.30	$255.30
Purchase #4	$57.76	6.868%	$61.727	$61.73	$61.75	$61.70
Purchase #5	$120.79	8.261%	$130.7685	$130.77	$130.75	$130.80
Purchase #6	$239.76	7.800%	$258.4613	$258.46	$258.45	$258.50
Purchase #7	$75.88	9.819%	$83.3307	$83.33	$83.35	$83.30
7 purchase totals =	$997.32		$1,071.2683	$1,071.27	$1,071.25	$1,071.30