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	$187.26	13.481%	$212.5045	$212.50	$212.50	$212.50
Purchase #2	$173.53	6.377%	$184.596	$184.60	$184.60	$184.60
Purchase #3	$129.37	11.447%	$144.179	$144.18	$144.20	$144.20
Purchase #4	$116.87	12.839%	$131.8749	$131.87	$131.85	$131.90
Purchase #5	$86.72	13.351%	$98.298	$98.30	$98.30	$98.30
Purchase #6	$152.84	3.275%	$157.8455	$157.85	$157.85	$157.80
Purchase #7	$64.75	13.342%	$73.3889	$73.39	$73.40	$73.40
7 purchase totals =	$911.34		$1,002.6868	$1,002.69	$1,002.70	$1,002.70