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	$96.96	10.231%	$106.88	$106.88	$106.90	$106.90
Purchase #2	$93.62	3.102%	$96.5241	$96.52	$96.50	$96.50
Purchase #3	$131.90	13.696%	$149.965	$149.97	$149.95	$150.00
Purchase #4	$214.59	11.135%	$238.4846	$238.48	$238.50	$238.50
Purchase #5	$143.95	4.283%	$150.1154	$150.12	$150.10	$150.10
Purchase #6	$137.28	13.865%	$156.3139	$156.31	$156.30	$156.30
Purchase #7	$45.26	12.320%	$50.836	$50.84	$50.85	$50.80
7 purchase totals =	$863.56		$949.1190	$949.12	$949.10	$949.10