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	$174.94	10.344%	$193.0358	$193.04	$193.05	$193.00
Purchase #2	$95.62	7.730%	$103.0114	$103.01	$103.00	$103.00
Purchase #3	$54.56	9.822%	$59.9189	$59.92	$59.90	$59.90
Purchase #4	$171.31	12.305%	$192.3897	$192.39	$192.40	$192.40
Purchase #5	$230.76	4.642%	$241.4719	$241.47	$241.45	$241.50
Purchase #6	$14.77	7.113%	$15.8206	$15.82	$15.80	$15.80
Purchase #7	$160.76	13.165%	$181.9241	$181.92	$181.90	$181.90
7 purchase totals =	$902.72		$987.5724	$987.57	$987.50	$987.50