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	$137.86	10.834%	$152.7958	$152.80	$152.80	$152.80
Purchase #2	$167.71	7.534%	$180.3453	$180.35	$180.35	$180.30
Purchase #3	$25.56	11.681%	$28.5457	$28.55	$28.55	$28.50
Purchase #4	$168.50	9.262%	$184.1065	$184.11	$184.10	$184.10
Purchase #5	$109.54	10.661%	$121.2181	$121.22	$121.20	$121.20
Purchase #6	$114.99	10.297%	$126.8305	$126.83	$126.85	$126.80
Purchase #7	$199.75	11.500%	$222.7213	$222.72	$222.70	$222.70
7 purchase totals =	$923.91		$1,016.5632	$1,016.58	$1,016.55	$1,016.40