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	$247.91	6.533%	$264.106	$264.11	$264.10	$264.10
Purchase #2	$149.59	8.534%	$162.356	$162.36	$162.35	$162.40
Purchase #3	$36.38	13.726%	$41.3735	$41.37	$41.35	$41.40
Purchase #4	$148.61	3.301%	$153.5156	$153.52	$153.50	$153.50
Purchase #5	$144.50	12.327%	$162.3125	$162.31	$162.30	$162.30
Purchase #6	$58.57	3.465%	$60.5995	$60.60	$60.60	$60.60
Purchase #7	$81.56	10.381%	$90.0267	$90.03	$90.05	$90.00
7 purchase totals =	$867.12		$934.2898	$934.30	$934.25	$934.30