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	$77.26	8.212%	$83.6046	$83.60	$83.60	$83.60
Purchase #2	$45.82	6.518%	$48.8065	$48.81	$48.80	$48.80
Purchase #3	$246.73	8.780%	$268.3929	$268.39	$268.40	$268.40
Purchase #4	$151.29	13.122%	$171.1423	$171.14	$171.15	$171.10
Purchase #5	$110.45	3.567%	$114.3898	$114.39	$114.40	$114.40
Purchase #6	$32.27	11.186%	$35.8797	$35.88	$35.90	$35.90
Purchase #7	$136.58	11.162%	$151.8251	$151.83	$151.85	$151.80
7 purchase totals =	$800.40		$874.0409	$874.04	$874.10	$874.00