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	$182.25	4.582%	$190.6007	$190.60	$190.60	$190.60
Purchase #2	$50.57	4.588%	$52.8902	$52.89	$52.90	$52.90
Purchase #3	$81.97	10.204%	$90.3342	$90.33	$90.35	$90.30
Purchase #4	$235.44	4.809%	$246.7623	$246.76	$246.75	$246.80
Purchase #5	$17.62	11.709%	$19.6831	$19.68	$19.70	$19.70
Purchase #6	$86.72	3.654%	$89.8887	$89.89	$89.90	$89.90
Purchase #7	$77.64	3.748%	$80.5499	$80.55	$80.55	$80.50
7 purchase totals =	$732.21		$770.7091	$770.70	$770.75	$770.70