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	$144.91	5.358%	$152.6743	$152.67	$152.65	$152.70
Purchase #2	$72.29	8.480%	$78.4202	$78.42	$78.40	$78.40
Purchase #3	$153.60	7.756%	$165.5132	$165.51	$165.50	$165.50
Purchase #4	$204.37	5.131%	$214.8562	$214.86	$214.85	$214.90
Purchase #5	$245.59	8.674%	$266.8925	$266.89	$266.90	$266.90
Purchase #6	$185.39	7.751%	$199.7596	$199.76	$199.75	$199.80
Purchase #7	$205.90	7.471%	$221.2828	$221.28	$221.30	$221.30
7 purchase totals =	$1,212.05		$1,299.3988	$1,299.39	$1,299.35	$1,299.50