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	$177.84	10.599%	$196.6893	$196.69	$196.70	$196.70
Purchase #2	$202.85	4.106%	$211.179	$211.18	$211.20	$211.20
Purchase #3	$119.34	7.706%	$128.5363	$128.54	$128.55	$128.50
Purchase #4	$155.49	13.378%	$176.2915	$176.29	$176.30	$176.30
Purchase #5	$26.48	7.791%	$28.5431	$28.54	$28.55	$28.50
Purchase #6	$231.63	6.284%	$246.1856	$246.19	$246.20	$246.20
Purchase #7	$82.86	8.152%	$89.6147	$89.61	$89.60	$89.60
7 purchase totals =	$996.49		$1,077.0395	$1,077.04	$1,077.10	$1,077.00