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	$180.30	5.480%	$190.1804	$190.18	$190.20	$190.20
Purchase #2	$212.64	4.456%	$222.1152	$222.12	$222.10	$222.10
Purchase #3	$83.83	12.478%	$94.2903	$94.29	$94.30	$94.30
Purchase #4	$32.48	13.430%	$36.8421	$36.84	$36.85	$36.80
Purchase #5	$19.56	11.248%	$21.7601	$21.76	$21.75	$21.80
Purchase #6	$48.98	11.295%	$54.5123	$54.51	$54.50	$54.50
Purchase #7	$72.41	12.839%	$81.7067	$81.71	$81.70	$81.70
7 purchase totals =	$650.20		$701.4071	$701.41	$701.40	$701.40