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	$112.82	5.772%	$119.332	$119.33	$119.35	$119.30
Purchase #2	$142.89	10.836%	$158.3736	$158.37	$158.35	$158.40
Purchase #3	$121.37	7.234%	$130.1499	$130.15	$130.15	$130.10
Purchase #4	$185.83	5.404%	$195.8723	$195.87	$195.85	$195.90
Purchase #5	$54.32	12.732%	$61.236	$61.24	$61.25	$61.20
Purchase #6	$120.72	8.718%	$131.2444	$131.24	$131.25	$131.20
Purchase #7	$72.91	4.779%	$76.3944	$76.39	$76.40	$76.40
7 purchase totals =	$810.86		$872.6026	$872.59	$872.60	$872.50