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	$193.56	5.648%	$204.4923	$204.49	$204.50	$204.50
Purchase #2	$40.51	11.434%	$45.1419	$45.14	$45.15	$45.10
Purchase #3	$160.93	12.424%	$180.9239	$180.92	$180.90	$180.90
Purchase #4	$59.73	4.674%	$62.5218	$62.52	$62.50	$62.50
Purchase #5	$240.59	10.616%	$266.131	$266.13	$266.15	$266.10
Purchase #6	$187.72	9.771%	$206.0621	$206.06	$206.05	$206.10
Purchase #7	$116.70	13.617%	$132.591	$132.59	$132.60	$132.60
7 purchase totals =	$999.74		$1,097.8640	$1,097.85	$1,097.85	$1,097.80