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	$70.89	3.455%	$73.3392	$73.34	$73.35	$73.30
Purchase #2	$63.81	11.507%	$71.1526	$71.15	$71.15	$71.20
Purchase #3	$53.97	7.304%	$57.912	$57.91	$57.90	$57.90
Purchase #4	$89.74	11.484%	$100.0457	$100.05	$100.05	$100.00
Purchase #5	$75.53	3.192%	$77.9409	$77.94	$77.95	$77.90
Purchase #6	$92.67	13.569%	$105.2444	$105.24	$105.25	$105.20
Purchase #7	$173.60	4.473%	$181.3651	$181.37	$181.35	$181.40
7 purchase totals =	$620.21		$666.9999	$667.00	$667.00	$666.90