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	$77.36	7.259%	$82.9756	$82.98	$83.00	$83.00
Purchase #2	$67.72	7.471%	$72.7794	$72.78	$72.80	$72.80
Purchase #3	$190.91	9.104%	$208.2904	$208.29	$208.30	$208.30
Purchase #4	$45.79	9.550%	$50.1629	$50.16	$50.15	$50.20
Purchase #5	$127.79	4.742%	$133.8498	$133.85	$133.85	$133.80
Purchase #6	$30.64	4.649%	$32.0645	$32.06	$32.05	$32.10
Purchase #7	$157.26	11.859%	$175.9095	$175.91	$175.90	$175.90
7 purchase totals =	$697.47		$756.0321	$756.03	$756.05	$756.10