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	$65.54	9.631%	$71.8522	$71.85	$71.85	$71.90
Purchase #2	$137.55	6.840%	$146.9584	$146.96	$146.95	$147.00
Purchase #3	$89.64	9.756%	$98.3853	$98.39	$98.40	$98.40
Purchase #4	$127.66	7.734%	$137.5332	$137.53	$137.55	$137.50
Purchase #5	$235.49	4.144%	$245.2487	$245.25	$245.25	$245.20
Purchase #6	$142.61	3.502%	$147.6042	$147.60	$147.60	$147.60
Purchase #7	$71.33	6.379%	$75.8801	$75.88	$75.90	$75.90
7 purchase totals =	$869.82		$923.4621	$923.46	$923.50	$923.50