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	$210.53	4.852%	$220.7449	$220.74	$220.75	$220.70
Purchase #2	$170.94	4.679%	$178.9383	$178.94	$178.95	$178.90
Purchase #3	$95.87	5.245%	$100.8984	$100.90	$100.90	$100.90
Purchase #4	$202.51	13.242%	$229.3264	$229.33	$229.35	$229.30
Purchase #5	$110.83	13.576%	$125.8763	$125.88	$125.90	$125.90
Purchase #6	$201.77	13.747%	$229.5073	$229.51	$229.50	$229.50
Purchase #7	$21.89	11.844%	$24.4827	$24.48	$24.50	$24.50
7 purchase totals =	$1,014.34		$1,109.7743	$1,109.78	$1,109.85	$1,109.70