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	$175.35	4.202%	$182.7182	$182.72	$182.70	$182.70
Purchase #2	$90.67	10.105%	$99.8322	$99.83	$99.85	$99.80
Purchase #3	$157.47	8.803%	$171.3321	$171.33	$171.35	$171.30
Purchase #4	$180.31	6.130%	$191.363	$191.36	$191.35	$191.40
Purchase #5	$71.33	10.613%	$78.9003	$78.90	$78.90	$78.90
Purchase #6	$189.25	13.744%	$215.2605	$215.26	$215.25	$215.30
Purchase #7	$196.56	11.386%	$218.9403	$218.94	$218.95	$218.90
7 purchase totals =	$1,060.94		$1,158.3466	$1,158.34	$1,158.35	$1,158.30