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	$89.49	4.793%	$93.7793	$93.78	$93.80	$93.80
Purchase #2	$95.47	9.191%	$104.2446	$104.24	$104.25	$104.20
Purchase #3	$37.61	8.607%	$40.8471	$40.85	$40.85	$40.80
Purchase #4	$229.60	7.358%	$246.494	$246.49	$246.50	$246.50
Purchase #5	$196.95	13.175%	$222.8982	$222.90	$222.90	$222.90
Purchase #6	$110.75	13.655%	$125.8729	$125.87	$125.85	$125.90
Purchase #7	$242.89	11.565%	$270.9802	$270.98	$271.00	$271.00
7 purchase totals =	$1,002.76		$1,105.1163	$1,105.11	$1,105.15	$1,105.10