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	$185.25	7.719%	$199.5494	$199.55	$199.55	$199.50
Purchase #2	$77.84	6.343%	$82.7774	$82.78	$82.80	$82.80
Purchase #3	$162.91	6.129%	$172.8948	$172.89	$172.90	$172.90
Purchase #4	$87.78	5.109%	$92.2647	$92.26	$92.25	$92.30
Purchase #5	$24.30	4.620%	$25.4227	$25.42	$25.40	$25.40
Purchase #6	$7.91	11.476%	$8.8178	$8.82	$8.80	$8.80
Purchase #7	$64.52	13.290%	$73.0947	$73.09	$73.10	$73.10
7 purchase totals =	$610.51		$654.8215	$654.81	$654.80	$654.80