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	$148.84	4.376%	$155.3532	$155.35	$155.35	$155.40
Purchase #2	$161.34	10.563%	$178.3823	$178.38	$178.40	$178.40
Purchase #3	$49.85	6.465%	$53.0728	$53.07	$53.05	$53.10
Purchase #4	$129.64	12.545%	$145.9033	$145.90	$145.90	$145.90
Purchase #5	$79.46	13.554%	$90.23	$90.23	$90.25	$90.20
Purchase #6	$35.26	8.425%	$38.2307	$38.23	$38.25	$38.20
Purchase #7	$85.57	3.593%	$88.6445	$88.64	$88.65	$88.60
7 purchase totals =	$689.96		$749.8168	$749.80	$749.85	$749.80