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	$36.80	11.127%	$40.8947	$40.89	$40.90	$40.90
Purchase #2	$28.50	10.575%	$31.5139	$31.51	$31.50	$31.50
Purchase #3	$16.53	11.815%	$18.483	$18.48	$18.50	$18.50
Purchase #4	$118.76	5.592%	$125.4011	$125.40	$125.40	$125.40
Purchase #5	$120.76	8.389%	$130.8906	$130.89	$130.90	$130.90
Purchase #6	$55.39	3.460%	$57.3065	$57.31	$57.30	$57.30
Purchase #7	$75.60	10.640%	$83.6438	$83.64	$83.65	$83.60
7 purchase totals =	$452.34		$488.1336	$488.12	$488.15	$488.10