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	$65.28	10.860%	$72.3694	$72.37	$72.35	$72.40
Purchase #2	$192.57	9.836%	$211.5112	$211.51	$211.50	$211.50
Purchase #3	$159.46	12.778%	$179.8358	$179.84	$179.85	$179.80
Purchase #4	$182.31	12.650%	$205.3722	$205.37	$205.35	$205.40
Purchase #5	$124.57	5.247%	$131.1062	$131.11	$131.10	$131.10
Purchase #6	$116.30	6.654%	$124.0386	$124.04	$124.05	$124.00
Purchase #7	$150.31	6.418%	$159.9569	$159.96	$159.95	$160.00
7 purchase totals =	$990.80		$1,084.1903	$1,084.20	$1,084.15	$1,084.20