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	$173.29	13.576%	$196.8159	$196.82	$196.80	$196.80
Purchase #2	$250.30	4.524%	$261.6236	$261.62	$261.60	$261.60
Purchase #3	$139.83	7.482%	$150.2921	$150.29	$150.30	$150.30
Purchase #4	$47.75	13.740%	$54.3109	$54.31	$54.30	$54.30
Purchase #5	$220.98	5.265%	$232.6146	$232.61	$232.60	$232.60
Purchase #6	$26.30	13.503%	$29.8513	$29.85	$29.85	$29.90
Purchase #7	$178.56	7.746%	$192.3913	$192.39	$192.40	$192.40
7 purchase totals =	$1,037.01		$1,117.8997	$1,117.89	$1,117.85	$1,117.90