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	$140.78	8.143%	$152.2437	$152.24	$152.25	$152.20
Purchase #2	$236.71	11.572%	$264.1021	$264.10	$264.10	$264.10
Purchase #3	$62.50	5.622%	$66.0138	$66.01	$66.00	$66.00
Purchase #4	$177.48	6.422%	$188.8778	$188.88	$188.90	$188.90
Purchase #5	$21.88	10.194%	$24.1104	$24.11	$24.10	$24.10
Purchase #6	$136.76	10.206%	$150.7177	$150.72	$150.70	$150.70
Purchase #7	$240.73	7.743%	$259.3697	$259.37	$259.35	$259.40
7 purchase totals =	$1,016.84		$1,105.4352	$1,105.43	$1,105.40	$1,105.40