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	$142.84	7.191%	$153.1116	$153.11	$153.10	$153.10
Purchase #2	$185.87	3.303%	$192.0093	$192.01	$192.00	$192.00
Purchase #3	$40.45	4.711%	$42.3556	$42.36	$42.35	$42.40
Purchase #4	$110.87	11.785%	$123.936	$123.94	$123.95	$123.90
Purchase #5	$142.42	9.738%	$156.2889	$156.29	$156.30	$156.30
Purchase #6	$175.49	3.598%	$181.8041	$181.80	$181.80	$181.80
Purchase #7	$59.57	10.164%	$65.6247	$65.62	$65.60	$65.60
7 purchase totals =	$857.51		$915.1302	$915.13	$915.10	$915.10