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	$202.42	10.121%	$222.9069	$222.91	$222.90	$222.90
Purchase #2	$66.98	11.316%	$74.5595	$74.56	$74.55	$74.60
Purchase #3	$71.88	7.528%	$77.2911	$77.29	$77.30	$77.30
Purchase #4	$188.83	10.126%	$207.9509	$207.95	$207.95	$208.00
Purchase #5	$184.86	6.352%	$196.6023	$196.60	$196.60	$196.60
Purchase #6	$113.94	12.481%	$128.1609	$128.16	$128.15	$128.20
Purchase #7	$76.65	13.292%	$86.8383	$86.84	$86.85	$86.80
7 purchase totals =	$905.56		$994.3099	$994.31	$994.30	$994.40