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	$146.69	4.492%	$153.2793	$153.28	$153.30	$153.30
Purchase #2	$170.90	9.560%	$187.238	$187.24	$187.25	$187.20
Purchase #3	$194.78	9.813%	$213.8938	$213.89	$213.90	$213.90
Purchase #4	$96.25	9.689%	$105.5757	$105.58	$105.60	$105.60
Purchase #5	$88.31	5.800%	$93.432	$93.43	$93.45	$93.40
Purchase #6	$154.82	11.209%	$172.1738	$172.17	$172.15	$172.20
Purchase #7	$38.36	11.755%	$42.8692	$42.87	$42.85	$42.90
7 purchase totals =	$890.11		$968.4618	$968.46	$968.50	$968.50