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	$164.81	3.535%	$170.636	$170.64	$170.65	$170.60
Purchase #2	$33.32	13.788%	$37.9142	$37.91	$37.90	$37.90
Purchase #3	$162.95	12.579%	$183.4475	$183.45	$183.45	$183.40
Purchase #4	$206.99	10.684%	$229.1048	$229.10	$229.10	$229.10
Purchase #5	$149.32	12.690%	$168.2687	$168.27	$168.25	$168.30
Purchase #6	$90.75	9.236%	$99.1317	$99.13	$99.15	$99.10
Purchase #7	$95.84	7.262%	$102.7999	$102.80	$102.80	$102.80
7 purchase totals =	$903.98		$991.3028	$991.30	$991.30	$991.20