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	$35.29	3.313%	$36.4592	$36.46	$36.45	$36.50
Purchase #2	$112.95	12.143%	$126.6655	$126.67	$126.65	$126.70
Purchase #3	$188.90	6.223%	$200.6552	$200.66	$200.65	$200.70
Purchase #4	$249.44	6.198%	$264.9003	$264.90	$264.90	$264.90
Purchase #5	$119.71	7.747%	$128.9839	$128.98	$129.00	$129.00
Purchase #6	$163.80	3.344%	$169.2775	$169.28	$169.30	$169.30
Purchase #7	$81.37	11.551%	$90.769	$90.77	$90.75	$90.80
7 purchase totals =	$951.46		$1,017.7106	$1,017.72	$1,017.70	$1,017.90