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	$174.25	8.667%	$189.3522	$189.35	$189.35	$189.40
Purchase #2	$220.40	12.202%	$247.2932	$247.29	$247.30	$247.30
Purchase #3	$70.96	11.166%	$78.8834	$78.88	$78.90	$78.90
Purchase #4	$214.85	3.770%	$222.9498	$222.95	$222.95	$222.90
Purchase #5	$152.84	10.484%	$168.8637	$168.86	$168.85	$168.90
Purchase #6	$200.76	7.310%	$215.4356	$215.44	$215.45	$215.40
Purchase #7	$94.49	11.392%	$105.2543	$105.25	$105.25	$105.30
7 purchase totals =	$1,128.55		$1,228.0322	$1,228.02	$1,228.05	$1,228.10