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	$127.66	4.507%	$133.4136	$133.41	$133.40	$133.40
Purchase #2	$98.67	4.412%	$103.0233	$103.02	$103.00	$103.00
Purchase #3	$130.86	13.176%	$148.1021	$148.10	$148.10	$148.10
Purchase #4	$19.31	6.131%	$20.4939	$20.49	$20.50	$20.50
Purchase #5	$84.71	11.650%	$94.5787	$94.58	$94.60	$94.60
Purchase #6	$213.51	6.327%	$227.0188	$227.02	$227.00	$227.00
Purchase #7	$109.53	13.789%	$124.6331	$124.63	$124.65	$124.60
7 purchase totals =	$784.25		$851.2635	$851.25	$851.25	$851.20