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	$134.79	5.477%	$142.1724	$142.17	$142.15	$142.20
Purchase #2	$170.84	8.549%	$185.4451	$185.45	$185.45	$185.40
Purchase #3	$183.94	7.584%	$197.89	$197.89	$197.90	$197.90
Purchase #4	$100.97	7.860%	$108.9062	$108.91	$108.90	$108.90
Purchase #5	$174.85	13.597%	$198.6244	$198.62	$198.60	$198.60
Purchase #6	$107.99	3.515%	$111.7858	$111.79	$111.80	$111.80
Purchase #7	$88.92	11.482%	$99.1298	$99.13	$99.15	$99.10
7 purchase totals =	$962.30		$1,043.9537	$1,043.96	$1,043.95	$1,043.90