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	$166.52	11.538%	$185.7331	$185.73	$185.75	$185.70
Purchase #2	$31.41	12.172%	$35.2332	$35.23	$35.25	$35.20
Purchase #3	$11.75	11.852%	$13.1426	$13.14	$13.15	$13.10
Purchase #4	$38.89	7.846%	$41.9413	$41.94	$41.95	$41.90
Purchase #5	$99.56	7.404%	$106.9314	$106.93	$106.95	$106.90
Purchase #6	$70.39	5.538%	$74.2882	$74.29	$74.30	$74.30
Purchase #7	$185.94	3.464%	$192.381	$192.38	$192.40	$192.40
7 purchase totals =	$604.46		$649.6508	$649.64	$649.75	$649.50