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	$104.74	6.859%	$111.9241	$111.92	$111.90	$111.90
Purchase #2	$211.29	12.856%	$238.4534	$238.45	$238.45	$238.50
Purchase #3	$238.96	3.432%	$247.1611	$247.16	$247.15	$247.20
Purchase #4	$9.99	11.785%	$11.1673	$11.17	$11.15	$11.20
Purchase #5	$39.83	5.737%	$42.115	$42.12	$42.10	$42.10
Purchase #6	$142.30	12.549%	$160.1572	$160.16	$160.15	$160.20
Purchase #7	$185.42	10.558%	$204.9966	$205.00	$205.00	$205.00
7 purchase totals =	$932.53		$1,015.9747	$1,015.98	$1,015.90	$1,016.10