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	$232.77	9.374%	$254.5899	$254.59	$254.60	$254.60
Purchase #2	$128.60	8.794%	$139.9091	$139.91	$139.90	$139.90
Purchase #3	$128.86	5.502%	$135.9499	$135.95	$135.95	$135.90
Purchase #4	$187.57	4.825%	$196.6203	$196.62	$196.60	$196.60
Purchase #5	$74.32	9.355%	$81.2726	$81.27	$81.25	$81.30
Purchase #6	$144.89	3.673%	$150.2118	$150.21	$150.20	$150.20
Purchase #7	$99.74	13.566%	$113.2707	$113.27	$113.25	$113.30
7 purchase totals =	$996.75		$1,071.8243	$1,071.82	$1,071.75	$1,071.80