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	$192.90	10.619%	$213.3841	$213.38	$213.40	$213.40
Purchase #2	$209.73	8.542%	$227.6451	$227.65	$227.65	$227.60
Purchase #3	$160.77	13.759%	$182.8903	$182.89	$182.90	$182.90
Purchase #4	$60.48	7.114%	$64.7825	$64.78	$64.80	$64.80
Purchase #5	$140.84	12.391%	$158.2915	$158.29	$158.30	$158.30
Purchase #6	$82.62	8.116%	$89.3254	$89.33	$89.35	$89.30
Purchase #7	$28.69	13.426%	$32.5419	$32.54	$32.55	$32.50
7 purchase totals =	$876.03		$968.8608	$968.86	$968.95	$968.80