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	$160.54	11.502%	$179.0053	$179.01	$179.00	$179.00
Purchase #2	$213.98	4.455%	$223.5128	$223.51	$223.50	$223.50
Purchase #3	$60.39	11.152%	$67.1247	$67.12	$67.10	$67.10
Purchase #4	$168.90	5.451%	$178.1067	$178.11	$178.10	$178.10
Purchase #5	$15.85	10.293%	$17.4814	$17.48	$17.50	$17.50
Purchase #6	$99.64	6.692%	$106.3079	$106.31	$106.30	$106.30
Purchase #7	$26.82	3.482%	$27.7539	$27.75	$27.75	$27.80
7 purchase totals =	$746.12		$799.2927	$799.29	$799.25	$799.30