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	$152.61	8.376%	$165.3926	$165.39	$165.40	$165.40
Purchase #2	$51.63	12.822%	$58.25	$58.25	$58.25	$58.30
Purchase #3	$60.48	7.265%	$64.8739	$64.87	$64.85	$64.90
Purchase #4	$135.49	9.211%	$147.97	$147.97	$147.95	$148.00
Purchase #5	$72.58	13.602%	$82.4523	$82.45	$82.45	$82.50
Purchase #6	$54.59	9.474%	$59.7619	$59.76	$59.75	$59.80
Purchase #7	$126.89	11.401%	$141.3567	$141.36	$141.35	$141.40
7 purchase totals =	$654.27		$720.0574	$720.05	$720.00	$720.30