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	$27.89	9.748%	$30.6087	$30.61	$30.60	$30.60
Purchase #2	$8.72	8.498%	$9.461	$9.46	$9.45	$9.50
Purchase #3	$104.31	7.134%	$111.7515	$111.75	$111.75	$111.80
Purchase #4	$77.47	10.404%	$85.53	$85.53	$85.55	$85.50
Purchase #5	$180.47	10.316%	$199.0873	$199.09	$199.10	$199.10
Purchase #6	$167.88	9.783%	$184.3037	$184.30	$184.30	$184.30
Purchase #7	$150.33	11.702%	$167.9216	$167.92	$167.90	$167.90
7 purchase totals =	$717.07		$788.6638	$788.66	$788.65	$788.70