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	$190.50	12.543%	$214.3944	$214.39	$214.40	$214.40
Purchase #2	$58.50	10.244%	$64.4927	$64.49	$64.50	$64.50
Purchase #3	$118.42	11.139%	$131.6108	$131.61	$131.60	$131.60
Purchase #4	$19.62	4.678%	$20.5378	$20.54	$20.55	$20.50
Purchase #5	$238.57	11.363%	$265.6787	$265.68	$265.70	$265.70
Purchase #6	$99.41	5.502%	$104.8795	$104.88	$104.90	$104.90
Purchase #7	$140.48	8.370%	$152.2382	$152.24	$152.25	$152.20
7 purchase totals =	$865.50		$953.8321	$953.83	$953.90	$953.80