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	$77.56	8.824%	$84.4039	$84.40	$84.40	$84.40
Purchase #2	$83.40	6.802%	$89.0729	$89.07	$89.05	$89.10
Purchase #3	$211.53	6.471%	$225.2181	$225.22	$225.20	$225.20
Purchase #4	$161.31	4.706%	$168.9012	$168.90	$168.90	$168.90
Purchase #5	$39.48	11.169%	$43.8895	$43.89	$43.90	$43.90
Purchase #6	$227.45	3.488%	$235.3835	$235.38	$235.40	$235.40
Purchase #7	$161.77	7.134%	$173.3107	$173.31	$173.30	$173.30
7 purchase totals =	$962.50		$1,020.1798	$1,020.17	$1,020.15	$1,020.20