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	$215.62	5.541%	$227.5675	$227.57	$227.55	$227.60
Purchase #2	$106.53	11.630%	$118.9194	$118.92	$118.90	$118.90
Purchase #3	$41.78	11.348%	$46.5212	$46.52	$46.50	$46.50
Purchase #4	$128.41	13.762%	$146.0818	$146.08	$146.10	$146.10
Purchase #5	$37.43	12.691%	$42.1802	$42.18	$42.20	$42.20
Purchase #6	$150.36	3.693%	$155.9128	$155.91	$155.90	$155.90
Purchase #7	$167.73	10.821%	$185.8801	$185.88	$185.90	$185.90
7 purchase totals =	$847.86		$923.0630	$923.06	$923.05	$923.10