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	$135.61	4.827%	$142.1559	$142.16	$142.15	$142.20
Purchase #2	$61.86	6.649%	$65.9731	$65.97	$65.95	$66.00
Purchase #3	$62.77	5.375%	$66.1439	$66.14	$66.15	$66.10
Purchase #4	$235.96	7.408%	$253.4399	$253.44	$253.45	$253.40
Purchase #5	$192.45	4.362%	$200.8447	$200.84	$200.85	$200.80
Purchase #6	$206.79	11.850%	$231.2946	$231.29	$231.30	$231.30
Purchase #7	$50.72	10.124%	$55.8549	$55.85	$55.85	$55.90
7 purchase totals =	$946.16		$1,015.7070	$1,015.69	$1,015.70	$1,015.70