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	$26.96	9.285%	$29.4632	$29.46	$29.45	$29.50
Purchase #2	$136.91	11.353%	$152.4534	$152.45	$152.45	$152.50
Purchase #3	$73.91	6.213%	$78.502	$78.50	$78.50	$78.50
Purchase #4	$206.83	12.365%	$232.4045	$232.40	$232.40	$232.40
Purchase #5	$109.67	13.593%	$124.5774	$124.58	$124.60	$124.60
Purchase #6	$166.47	9.773%	$182.7391	$182.74	$182.75	$182.70
Purchase #7	$229.59	6.802%	$245.2067	$245.21	$245.20	$245.20
7 purchase totals =	$950.34		$1,045.3463	$1,045.34	$1,045.35	$1,045.40