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	$58.85	3.211%	$60.7397	$60.74	$60.75	$60.70
Purchase #2	$63.53	13.338%	$72.0036	$72.00	$72.00	$72.00
Purchase #3	$126.84	10.460%	$140.1075	$140.11	$140.10	$140.10
Purchase #4	$171.84	11.501%	$191.6033	$191.60	$191.60	$191.60
Purchase #5	$89.57	11.703%	$100.0524	$100.05	$100.05	$100.10
Purchase #6	$221.85	4.175%	$231.1122	$231.11	$231.10	$231.10
Purchase #7	$49.72	11.758%	$55.5661	$55.57	$55.55	$55.60
7 purchase totals =	$782.20		$851.1848	$851.18	$851.15	$851.20