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	$212.33	11.722%	$237.2193	$237.22	$237.20	$237.20
Purchase #2	$149.88	13.803%	$170.5679	$170.57	$170.55	$170.60
Purchase #3	$31.44	4.775%	$32.9413	$32.94	$32.95	$32.90
Purchase #4	$106.40	5.520%	$112.2733	$112.27	$112.25	$112.30
Purchase #5	$144.65	7.392%	$155.3425	$155.34	$155.35	$155.30
Purchase #6	$56.89	5.188%	$59.8415	$59.84	$59.85	$59.80
Purchase #7	$248.87	10.403%	$274.7599	$274.76	$274.75	$274.80
7 purchase totals =	$950.46		$1,042.9457	$1,042.94	$1,042.90	$1,042.90