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	$243.53	3.739%	$252.6356	$252.64	$252.65	$252.60
Purchase #2	$166.63	4.663%	$174.4	$174.40	$174.40	$174.40
Purchase #3	$106.78	4.353%	$111.4281	$111.43	$111.45	$111.40
Purchase #4	$196.58	8.439%	$213.1694	$213.17	$213.15	$213.20
Purchase #5	$77.72	5.854%	$82.2697	$82.27	$82.25	$82.30
Purchase #6	$241.70	8.873%	$263.146	$263.15	$263.15	$263.10
Purchase #7	$25.38	3.742%	$26.3297	$26.33	$26.35	$26.30
7 purchase totals =	$1,058.32		$1,123.3785	$1,123.39	$1,123.40	$1,123.30