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	$131.62	12.343%	$147.8659	$147.87	$147.85	$147.90
Purchase #2	$123.62	4.107%	$128.6971	$128.70	$128.70	$128.70
Purchase #3	$156.41	11.164%	$173.8716	$173.87	$173.85	$173.90
Purchase #4	$131.90	7.215%	$141.4166	$141.42	$141.40	$141.40
Purchase #5	$143.64	4.581%	$150.2201	$150.22	$150.20	$150.20
Purchase #6	$95.83	12.162%	$107.4848	$107.48	$107.50	$107.50
Purchase #7	$213.37	10.367%	$235.4901	$235.49	$235.50	$235.50
7 purchase totals =	$996.39		$1,085.0462	$1,085.05	$1,085.00	$1,085.10