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	$110.60	12.111%	$123.9948	$123.99	$124.00	$124.00
Purchase #2	$234.89	4.789%	$246.1389	$246.14	$246.15	$246.10
Purchase #3	$182.93	9.569%	$200.4346	$200.43	$200.45	$200.40
Purchase #4	$156.85	7.173%	$168.1009	$168.10	$168.10	$168.10
Purchase #5	$60.89	10.671%	$67.3876	$67.39	$67.40	$67.40
Purchase #6	$188.71	3.662%	$195.6206	$195.62	$195.60	$195.60
Purchase #7	$45.44	11.361%	$50.6024	$50.60	$50.60	$50.60
7 purchase totals =	$980.31		$1,052.2798	$1,052.27	$1,052.30	$1,052.20