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	$68.71	11.281%	$76.4612	$76.46	$76.45	$76.50
Purchase #2	$40.81	10.355%	$45.0359	$45.04	$45.05	$45.00
Purchase #3	$175.60	7.309%	$188.4346	$188.43	$188.45	$188.40
Purchase #4	$199.96	4.717%	$209.3921	$209.39	$209.40	$209.40
Purchase #5	$18.77	12.280%	$21.075	$21.08	$21.10	$21.10
Purchase #6	$222.42	4.276%	$231.9307	$231.93	$231.95	$231.90
Purchase #7	$49.57	6.722%	$52.9021	$52.90	$52.90	$52.90
7 purchase totals =	$775.84		$825.2316	$825.23	$825.30	$825.20