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	$161.44	12.360%	$181.394	$181.39	$181.40	$181.40
Purchase #2	$103.89	7.604%	$111.7898	$111.79	$111.80	$111.80
Purchase #3	$82.74	8.225%	$89.5454	$89.55	$89.55	$89.50
Purchase #4	$119.65	4.601%	$125.1551	$125.16	$125.15	$125.20
Purchase #5	$225.95	7.460%	$242.8059	$242.81	$242.80	$242.80
Purchase #6	$166.43	6.602%	$177.4177	$177.42	$177.40	$177.40
Purchase #7	$175.77	5.492%	$185.4233	$185.42	$185.40	$185.40
7 purchase totals =	$1,035.87		$1,113.5312	$1,113.54	$1,113.50	$1,113.50