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	$48.87	11.837%	$54.6547	$54.65	$54.65	$54.70
Purchase #2	$116.74	7.802%	$125.8481	$125.85	$125.85	$125.80
Purchase #3	$71.73	13.780%	$81.6144	$81.61	$81.60	$81.60
Purchase #4	$92.89	13.328%	$105.2704	$105.27	$105.25	$105.30
Purchase #5	$147.79	9.417%	$161.7074	$161.71	$161.70	$161.70
Purchase #6	$105.61	4.136%	$109.978	$109.98	$110.00	$110.00
Purchase #7	$61.27	6.544%	$65.2795	$65.28	$65.30	$65.30
7 purchase totals =	$644.90		$704.3525	$704.35	$704.35	$704.40