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	$244.90	4.697%	$256.403	$256.40	$256.40	$256.40
Purchase #2	$168.89	6.522%	$179.905	$179.91	$179.90	$179.90
Purchase #3	$146.73	6.456%	$156.2029	$156.20	$156.20	$156.20
Purchase #4	$106.34	11.155%	$118.2022	$118.20	$118.20	$118.20
Purchase #5	$88.89	10.524%	$98.2448	$98.24	$98.25	$98.20
Purchase #6	$14.74	6.703%	$15.728	$15.73	$15.75	$15.70
Purchase #7	$19.92	7.747%	$21.4632	$21.46	$21.45	$21.50
7 purchase totals =	$790.41		$846.1491	$846.14	$846.15	$846.10