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	$48.91	8.635%	$53.1334	$53.13	$53.15	$53.10
Purchase #2	$38.78	4.194%	$40.4064	$40.41	$40.40	$40.40
Purchase #3	$98.29	5.366%	$103.5642	$103.56	$103.55	$103.60
Purchase #4	$211.81	4.259%	$220.831	$220.83	$220.85	$220.80
Purchase #5	$149.35	11.285%	$166.2041	$166.20	$166.20	$166.20
Purchase #6	$215.58	10.736%	$238.7247	$238.72	$238.70	$238.70
Purchase #7	$243.46	10.638%	$269.3593	$269.36	$269.35	$269.40
7 purchase totals =	$1,006.18		$1,092.2231	$1,092.21	$1,092.20	$1,092.20