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	$145.38	9.260%	$158.8422	$158.84	$158.85	$158.80
Purchase #2	$170.98	5.505%	$180.3924	$180.39	$180.40	$180.40
Purchase #3	$120.69	9.339%	$131.9612	$131.96	$131.95	$132.00
Purchase #4	$6.84	5.790%	$7.236	$7.24	$7.25	$7.20
Purchase #5	$42.59	10.725%	$47.1578	$47.16	$47.15	$47.20
Purchase #6	$18.74	8.682%	$20.367	$20.37	$20.35	$20.40
Purchase #7	$135.48	11.859%	$151.5466	$151.55	$151.55	$151.50
7 purchase totals =	$640.70		$697.5032	$697.51	$697.50	$697.50