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	$92.51	7.650%	$99.587	$99.59	$99.60	$99.60
Purchase #2	$152.58	6.747%	$162.8746	$162.87	$162.85	$162.90
Purchase #3	$54.89	4.816%	$57.5335	$57.53	$57.55	$57.50
Purchase #4	$129.35	12.194%	$145.1229	$145.12	$145.10	$145.10
Purchase #5	$119.87	3.145%	$123.6399	$123.64	$123.65	$123.60
Purchase #6	$147.88	11.784%	$165.3062	$165.31	$165.30	$165.30
Purchase #7	$227.56	12.847%	$256.7946	$256.79	$256.80	$256.80
7 purchase totals =	$924.64		$1,010.8587	$1,010.85	$1,010.85	$1,010.80