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	$73.52	3.108%	$75.805	$75.81	$75.80	$75.80
Purchase #2	$95.26	8.812%	$103.6543	$103.65	$103.65	$103.70
Purchase #3	$91.37	9.281%	$99.85	$99.85	$99.85	$99.90
Purchase #4	$110.83	11.747%	$123.8492	$123.85	$123.85	$123.80
Purchase #5	$209.78	4.133%	$218.4502	$218.45	$218.45	$218.50
Purchase #6	$142.31	6.550%	$151.6313	$151.63	$151.65	$151.60
Purchase #7	$47.76	9.682%	$52.3841	$52.38	$52.40	$52.40
7 purchase totals =	$770.83		$825.6241	$825.62	$825.65	$825.70