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	$148.25	6.188%	$157.4237	$157.42	$157.40	$157.40
Purchase #2	$24.41	6.254%	$25.9366	$25.94	$25.95	$25.90
Purchase #3	$53.31	5.166%	$56.064	$56.06	$56.05	$56.10
Purchase #4	$197.72	10.723%	$218.9215	$218.92	$218.90	$218.90
Purchase #5	$73.89	12.188%	$82.8957	$82.90	$82.90	$82.90
Purchase #6	$199.94	8.114%	$216.1631	$216.16	$216.15	$216.20
Purchase #7	$148.52	11.728%	$165.9384	$165.94	$165.95	$165.90
7 purchase totals =	$846.04		$923.3430	$923.34	$923.30	$923.30