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	$58.79	3.830%	$61.0417	$61.04	$61.05	$61.00
Purchase #2	$145.96	3.699%	$151.3591	$151.36	$151.35	$151.40
Purchase #3	$35.68	9.655%	$39.1249	$39.12	$39.10	$39.10
Purchase #4	$118.78	11.599%	$132.5573	$132.56	$132.55	$132.60
Purchase #5	$109.59	4.428%	$114.4426	$114.44	$114.45	$114.40
Purchase #6	$208.52	11.114%	$231.6949	$231.69	$231.70	$231.70
Purchase #7	$81.90	9.342%	$89.5511	$89.55	$89.55	$89.60
7 purchase totals =	$759.22		$819.7716	$819.76	$819.75	$819.80