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	$128.25	12.759%	$144.6134	$144.61	$144.60	$144.60
Purchase #2	$226.36	7.191%	$242.6375	$242.64	$242.65	$242.60
Purchase #3	$240.82	5.190%	$253.3186	$253.32	$253.30	$253.30
Purchase #4	$147.76	6.646%	$157.5801	$157.58	$157.60	$157.60
Purchase #5	$77.29	5.789%	$81.7643	$81.76	$81.75	$81.80
Purchase #6	$126.82	3.830%	$131.6772	$131.68	$131.70	$131.70
Purchase #7	$118.86	3.738%	$123.303	$123.30	$123.30	$123.30
7 purchase totals =	$1,066.16		$1,134.8941	$1,134.89	$1,134.90	$1,134.90