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	$170.74	6.799%	$182.3486	$182.35	$182.35	$182.30
Purchase #2	$30.92	5.467%	$32.6104	$32.61	$32.60	$32.60
Purchase #3	$90.61	7.613%	$97.5081	$97.51	$97.50	$97.50
Purchase #4	$214.65	13.470%	$243.5634	$243.56	$243.55	$243.60
Purchase #5	$30.38	3.667%	$31.494	$31.49	$31.50	$31.50
Purchase #6	$159.30	12.847%	$179.7653	$179.77	$179.75	$179.80
Purchase #7	$58.68	7.129%	$62.8633	$62.86	$62.85	$62.90
7 purchase totals =	$755.28		$830.1531	$830.15	$830.10	$830.20