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	$188.88	10.154%	$208.0589	$208.06	$208.05	$208.10
Purchase #2	$172.84	13.780%	$196.6574	$196.66	$196.65	$196.70
Purchase #3	$221.69	11.633%	$247.4792	$247.48	$247.50	$247.50
Purchase #4	$140.37	9.126%	$153.1802	$153.18	$153.20	$153.20
Purchase #5	$108.60	5.809%	$114.9086	$114.91	$114.90	$114.90
Purchase #6	$227.86	5.331%	$240.0072	$240.01	$240.00	$240.00
Purchase #7	$64.96	4.102%	$67.6247	$67.62	$67.60	$67.60
7 purchase totals =	$1,125.20		$1,227.9162	$1,227.92	$1,227.90	$1,228.00