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	$180.56	7.684%	$194.4342	$194.43	$194.45	$194.40
Purchase #2	$83.32	13.159%	$94.2841	$94.28	$94.30	$94.30
Purchase #3	$26.74	3.510%	$27.6786	$27.68	$27.70	$27.70
Purchase #4	$148.76	4.614%	$155.6238	$155.62	$155.60	$155.60
Purchase #5	$222.38	3.456%	$230.0655	$230.07	$230.05	$230.10
Purchase #6	$52.88	12.323%	$59.3964	$59.40	$59.40	$59.40
Purchase #7	$66.69	7.217%	$71.503	$71.50	$71.50	$71.50
7 purchase totals =	$781.33		$832.9856	$832.98	$833.00	$833.00