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	$245.56	7.713%	$264.5	$264.50	$264.50	$264.50
Purchase #2	$81.40	13.234%	$92.1725	$92.17	$92.15	$92.20
Purchase #3	$157.34	5.302%	$165.6822	$165.68	$165.70	$165.70
Purchase #4	$173.34	5.735%	$183.281	$183.28	$183.30	$183.30
Purchase #5	$16.65	3.453%	$17.2249	$17.22	$17.20	$17.20
Purchase #6	$52.83	12.151%	$59.2494	$59.25	$59.25	$59.20
Purchase #7	$152.59	6.374%	$162.3161	$162.32	$162.30	$162.30
7 purchase totals =	$879.71		$944.4261	$944.42	$944.40	$944.40