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	$59.73	9.451%	$65.3751	$65.38	$65.40	$65.40
Purchase #2	$227.96	5.329%	$240.108	$240.11	$240.10	$240.10
Purchase #3	$99.43	4.282%	$103.6876	$103.69	$103.70	$103.70
Purchase #4	$139.83	7.499%	$150.3159	$150.32	$150.30	$150.30
Purchase #5	$18.40	11.283%	$20.4761	$20.48	$20.50	$20.50
Purchase #6	$159.47	4.813%	$167.1453	$167.15	$167.15	$167.10
Purchase #7	$164.69	10.686%	$182.2888	$182.29	$182.30	$182.30
7 purchase totals =	$869.51		$929.3968	$929.42	$929.45	$929.40