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	$51.46	5.377%	$54.227	$54.23	$54.25	$54.20
Purchase #2	$72.41	11.177%	$80.5033	$80.50	$80.50	$80.50
Purchase #3	$18.52	12.384%	$20.8135	$20.81	$20.80	$20.80
Purchase #4	$6.43	12.253%	$7.2179	$7.22	$7.20	$7.20
Purchase #5	$246.49	4.193%	$256.8253	$256.83	$256.85	$256.80
Purchase #6	$28.71	9.324%	$31.3869	$31.39	$31.40	$31.40
Purchase #7	$91.40	13.187%	$103.4529	$103.45	$103.45	$103.50
7 purchase totals =	$515.42		$554.4268	$554.43	$554.45	$554.40