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	$45.83	6.793%	$48.9432	$48.94	$48.95	$48.90
Purchase #2	$201.36	5.646%	$212.7288	$212.73	$212.75	$212.70
Purchase #3	$180.30	9.853%	$198.065	$198.07	$198.05	$198.10
Purchase #4	$105.97	13.293%	$120.0566	$120.06	$120.05	$120.10
Purchase #5	$55.88	6.759%	$59.6569	$59.66	$59.65	$59.70
Purchase #6	$152.46	8.563%	$165.5151	$165.52	$165.50	$165.50
Purchase #7	$50.62	12.419%	$56.9065	$56.91	$56.90	$56.90
7 purchase totals =	$792.42		$861.8721	$861.89	$861.85	$861.90