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	$136.90	12.229%	$153.6415	$153.64	$153.65	$153.60
Purchase #2	$234.63	11.562%	$261.7579	$261.76	$261.75	$261.80
Purchase #3	$75.83	9.147%	$82.7662	$82.77	$82.75	$82.80
Purchase #4	$63.98	11.616%	$71.4119	$71.41	$71.40	$71.40
Purchase #5	$37.86	7.783%	$40.8066	$40.81	$40.80	$40.80
Purchase #6	$102.25	3.854%	$106.1907	$106.19	$106.20	$106.20
Purchase #7	$146.27	3.377%	$151.2095	$151.21	$151.20	$151.20
7 purchase totals =	$797.72		$867.7843	$867.79	$867.75	$867.80