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	$38.85	11.472%	$43.3069	$43.31	$43.30	$43.30
Purchase #2	$198.97	13.128%	$225.0908	$225.09	$225.10	$225.10
Purchase #3	$35.39	7.728%	$38.1249	$38.12	$38.10	$38.10
Purchase #4	$196.46	13.539%	$223.0587	$223.06	$223.05	$223.10
Purchase #5	$5.42	4.684%	$5.6739	$5.67	$5.65	$5.70
Purchase #6	$218.53	3.390%	$225.9382	$225.94	$225.95	$225.90
Purchase #7	$39.81	7.133%	$42.6496	$42.65	$42.65	$42.60
7 purchase totals =	$733.43		$803.8430	$803.84	$803.80	$803.80