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	$49.38	8.355%	$53.5057	$53.51	$53.50	$53.50
Purchase #2	$59.61	6.589%	$63.5377	$63.54	$63.55	$63.50
Purchase #3	$58.37	10.376%	$64.4265	$64.43	$64.45	$64.40
Purchase #4	$77.57	13.865%	$88.3251	$88.33	$88.35	$88.30
Purchase #5	$182.93	5.456%	$192.9107	$192.91	$192.90	$192.90
Purchase #6	$166.65	13.342%	$188.8844	$188.88	$188.90	$188.90
Purchase #7	$149.29	13.374%	$169.256	$169.26	$169.25	$169.30
7 purchase totals =	$743.80		$820.8461	$820.86	$820.90	$820.80