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	$196.65	6.334%	$209.1058	$209.11	$209.10	$209.10
Purchase #2	$87.70	13.202%	$99.2782	$99.28	$99.30	$99.30
Purchase #3	$90.70	9.415%	$99.2394	$99.24	$99.25	$99.20
Purchase #4	$172.54	10.553%	$190.7481	$190.75	$190.75	$190.70
Purchase #5	$138.61	4.533%	$144.8932	$144.89	$144.90	$144.90
Purchase #6	$225.40	6.660%	$240.4116	$240.41	$240.40	$240.40
Purchase #7	$40.56	13.813%	$46.1626	$46.16	$46.15	$46.20
7 purchase totals =	$952.16		$1,029.8389	$1,029.84	$1,029.85	$1,029.80