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	$236.74	4.170%	$246.6121	$246.61	$246.60	$246.60
Purchase #2	$203.65	7.594%	$219.1152	$219.12	$219.10	$219.10
Purchase #3	$62.56	12.334%	$70.2762	$70.28	$70.30	$70.30
Purchase #4	$52.54	4.137%	$54.7136	$54.71	$54.70	$54.70
Purchase #5	$215.89	6.816%	$230.6051	$230.61	$230.60	$230.60
Purchase #6	$78.87	8.435%	$85.5227	$85.52	$85.50	$85.50
Purchase #7	$161.47	3.811%	$167.6236	$167.62	$167.60	$167.60
7 purchase totals =	$1,011.72		$1,074.4685	$1,074.47	$1,074.40	$1,074.40