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	$200.52	9.287%	$219.1423	$219.14	$219.15	$219.10
Purchase #2	$165.72	5.784%	$175.3052	$175.31	$175.30	$175.30
Purchase #3	$71.71	11.597%	$80.0262	$80.03	$80.05	$80.00
Purchase #4	$242.40	12.709%	$273.2066	$273.21	$273.20	$273.20
Purchase #5	$69.79	11.799%	$78.0245	$78.02	$78.00	$78.00
Purchase #6	$79.26	8.366%	$85.8909	$85.89	$85.90	$85.90
Purchase #7	$203.83	3.229%	$210.4117	$210.41	$210.40	$210.40
7 purchase totals =	$1,033.23		$1,122.0074	$1,122.01	$1,122.00	$1,121.90