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	$183.83	9.130%	$200.6137	$200.61	$200.60	$200.60
Purchase #2	$160.56	11.559%	$179.1191	$179.12	$179.10	$179.10
Purchase #3	$88.40	6.676%	$94.3016	$94.30	$94.30	$94.30
Purchase #4	$80.61	5.316%	$84.8952	$84.90	$84.90	$84.90
Purchase #5	$125.90	9.406%	$137.7422	$137.74	$137.75	$137.70
Purchase #6	$181.26	5.290%	$190.8487	$190.85	$190.85	$190.80
Purchase #7	$176.64	8.399%	$191.476	$191.48	$191.50	$191.50
7 purchase totals =	$997.20		$1,078.9965	$1,079.00	$1,079.00	$1,078.90