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	$86.83	5.761%	$91.8323	$91.83	$91.85	$91.80
Purchase #2	$72.58	5.686%	$76.7069	$76.71	$76.70	$76.70
Purchase #3	$85.46	5.470%	$90.1347	$90.13	$90.15	$90.10
Purchase #4	$86.30	11.205%	$95.9699	$95.97	$95.95	$96.00
Purchase #5	$97.91	13.783%	$111.4049	$111.40	$111.40	$111.40
Purchase #6	$97.86	9.572%	$107.2272	$107.23	$107.25	$107.20
Purchase #7	$242.40	7.125%	$259.671	$259.67	$259.65	$259.70
7 purchase totals =	$769.34		$832.9469	$832.94	$832.95	$832.90