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	$220.40	4.197%	$229.6502	$229.65	$229.65	$229.70
Purchase #2	$213.62	3.662%	$221.4428	$221.44	$221.45	$221.40
Purchase #3	$100.51	9.487%	$110.0454	$110.05	$110.05	$110.00
Purchase #4	$152.27	6.281%	$161.8341	$161.83	$161.85	$161.80
Purchase #5	$85.57	4.473%	$89.3975	$89.40	$89.40	$89.40
Purchase #6	$65.53	3.549%	$67.8557	$67.86	$67.85	$67.90
Purchase #7	$73.44	7.227%	$78.7475	$78.75	$78.75	$78.70
7 purchase totals =	$911.34		$958.9732	$958.98	$959.00	$958.90