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	$54.98	7.428%	$59.0639	$59.06	$59.05	$59.10
Purchase #2	$234.59	10.871%	$260.0923	$260.09	$260.10	$260.10
Purchase #3	$221.31	6.257%	$235.1574	$235.16	$235.15	$235.20
Purchase #4	$51.65	10.504%	$57.0753	$57.08	$57.10	$57.10
Purchase #5	$250.85	9.843%	$275.5412	$275.54	$275.55	$275.50
Purchase #6	$160.75	12.514%	$180.8663	$180.87	$180.85	$180.90
Purchase #7	$6.59	5.843%	$6.9751	$6.98	$7.00	$7.00
7 purchase totals =	$980.72		$1,074.7715	$1,074.78	$1,074.80	$1,074.90