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	$213.48	10.194%	$235.2422	$235.24	$235.25	$235.20
Purchase #2	$33.90	11.772%	$37.8907	$37.89	$37.90	$37.90
Purchase #3	$170.55	5.807%	$180.4538	$180.45	$180.45	$180.50
Purchase #4	$42.56	8.259%	$46.075	$46.08	$46.10	$46.10
Purchase #5	$175.49	7.261%	$188.2323	$188.23	$188.25	$188.20
Purchase #6	$185.47	7.636%	$199.6325	$199.63	$199.65	$199.60
Purchase #7	$181.38	5.266%	$190.9315	$190.93	$190.95	$190.90
7 purchase totals =	$1,002.83		$1,078.4580	$1,078.45	$1,078.55	$1,078.40