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	$179.86	6.328%	$191.2415	$191.24	$191.25	$191.20
Purchase #2	$72.44	6.386%	$77.066	$77.07	$77.05	$77.10
Purchase #3	$48.72	9.329%	$53.2651	$53.27	$53.25	$53.30
Purchase #4	$88.34	4.638%	$92.4372	$92.44	$92.45	$92.40
Purchase #5	$62.97	6.169%	$66.8546	$66.85	$66.85	$66.90
Purchase #6	$65.48	9.541%	$71.7274	$71.73	$71.75	$71.70
Purchase #7	$231.43	4.802%	$242.5433	$242.54	$242.55	$242.50
7 purchase totals =	$749.24		$795.1351	$795.14	$795.15	$795.10