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	$141.76	4.551%	$148.2115	$148.21	$148.20	$148.20
Purchase #2	$220.46	6.518%	$234.8296	$234.83	$234.85	$234.80
Purchase #3	$91.87	8.346%	$99.5375	$99.54	$99.55	$99.50
Purchase #4	$47.29	13.233%	$53.5479	$53.55	$53.55	$53.50
Purchase #5	$123.35	13.272%	$139.721	$139.72	$139.70	$139.70
Purchase #6	$146.69	5.199%	$154.3164	$154.32	$154.30	$154.30
Purchase #7	$226.53	12.738%	$255.3854	$255.39	$255.40	$255.40
7 purchase totals =	$997.95		$1,085.5493	$1,085.56	$1,085.55	$1,085.40