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	$223.74	10.872%	$248.065	$248.07	$248.05	$248.10
Purchase #2	$91.65	10.865%	$101.6078	$101.61	$101.60	$101.60
Purchase #3	$115.98	12.821%	$130.8498	$130.85	$130.85	$130.80
Purchase #4	$163.32	10.170%	$179.9296	$179.93	$179.95	$179.90
Purchase #5	$196.46	7.758%	$211.7014	$211.70	$211.70	$211.70
Purchase #6	$48.80	11.358%	$54.3427	$54.34	$54.35	$54.30
Purchase #7	$180.28	11.267%	$200.5921	$200.59	$200.60	$200.60
7 purchase totals =	$1,020.23		$1,127.0884	$1,127.09	$1,127.10	$1,127.00