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	$212.48	4.817%	$222.7152	$222.72	$222.70	$222.70
Purchase #2	$132.59	13.867%	$150.9763	$150.98	$151.00	$151.00
Purchase #3	$96.81	13.748%	$110.1194	$110.12	$110.10	$110.10
Purchase #4	$247.69	4.330%	$258.415	$258.42	$258.40	$258.40
Purchase #5	$29.59	3.669%	$30.6757	$30.68	$30.70	$30.70
Purchase #6	$116.94	10.240%	$128.9147	$128.91	$128.90	$128.90
Purchase #7	$167.31	5.578%	$176.6426	$176.64	$176.65	$176.60
7 purchase totals =	$1,003.41		$1,078.4589	$1,078.47	$1,078.45	$1,078.40