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	$147.43	5.378%	$155.3588	$155.36	$155.35	$155.40
Purchase #2	$99.38	3.657%	$103.0143	$103.01	$103.00	$103.00
Purchase #3	$60.67	10.781%	$67.2108	$67.21	$67.20	$67.20
Purchase #4	$38.98	6.216%	$41.403	$41.40	$41.40	$41.40
Purchase #5	$203.88	6.226%	$216.5736	$216.57	$216.55	$216.60
Purchase #6	$212.54	7.229%	$227.9045	$227.90	$227.90	$227.90
Purchase #7	$74.34	12.751%	$83.8191	$83.82	$83.80	$83.80
7 purchase totals =	$837.22		$895.2841	$895.27	$895.20	$895.30