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	$35.39	8.654%	$38.4527	$38.45	$38.45	$38.50
Purchase #2	$104.55	5.143%	$109.927	$109.93	$109.95	$109.90
Purchase #3	$214.66	13.579%	$243.8087	$243.81	$243.80	$243.80
Purchase #4	$152.51	8.799%	$165.9294	$165.93	$165.95	$165.90
Purchase #5	$100.76	11.796%	$112.6456	$112.65	$112.65	$112.60
Purchase #6	$154.77	7.573%	$166.4907	$166.49	$166.50	$166.50
Purchase #7	$145.65	11.166%	$161.9133	$161.91	$161.90	$161.90
7 purchase totals =	$908.29		$999.1674	$999.17	$999.20	$999.10