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	$57.75	6.337%	$61.4096	$61.41	$61.40	$61.40
Purchase #2	$85.32	13.268%	$96.6403	$96.64	$96.65	$96.60
Purchase #3	$35.34	10.821%	$39.1641	$39.16	$39.15	$39.20
Purchase #4	$124.50	13.115%	$140.8282	$140.83	$140.85	$140.80
Purchase #5	$124.81	8.104%	$134.9246	$134.92	$134.90	$134.90
Purchase #6	$157.69	4.153%	$164.2389	$164.24	$164.25	$164.20
Purchase #7	$235.77	11.141%	$262.0371	$262.04	$262.05	$262.00
7 purchase totals =	$821.18		$899.2428	$899.24	$899.25	$899.10