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	$76.49	3.775%	$79.3775	$79.38	$79.40	$79.40
Purchase #2	$149.29	9.764%	$163.8667	$163.87	$163.85	$163.90
Purchase #3	$91.82	9.804%	$100.822	$100.82	$100.80	$100.80
Purchase #4	$165.37	8.534%	$179.4827	$179.48	$179.50	$179.50
Purchase #5	$206.73	13.169%	$233.9543	$233.95	$233.95	$234.00
Purchase #6	$121.70	4.625%	$127.3286	$127.33	$127.35	$127.30
Purchase #7	$185.38	13.303%	$210.0411	$210.04	$210.05	$210.00
7 purchase totals =	$996.78		$1,094.8729	$1,094.87	$1,094.90	$1,094.90