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	$182.93	4.281%	$190.7612	$190.76	$190.75	$190.80
Purchase #2	$46.56	12.370%	$52.3195	$52.32	$52.30	$52.30
Purchase #3	$156.51	3.612%	$162.1631	$162.16	$162.15	$162.20
Purchase #4	$40.99	4.458%	$42.8173	$42.82	$42.80	$42.80
Purchase #5	$213.72	4.329%	$222.9719	$222.97	$222.95	$223.00
Purchase #6	$29.30	7.161%	$31.3982	$31.40	$31.40	$31.40
Purchase #7	$215.59	13.790%	$245.3199	$245.32	$245.30	$245.30
7 purchase totals =	$885.60		$947.7511	$947.75	$947.65	$947.80