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	$193.69	5.546%	$204.432	$204.43	$204.45	$204.40
Purchase #2	$45.79	7.638%	$49.2874	$49.29	$49.30	$49.30
Purchase #3	$78.42	13.284%	$88.8373	$88.84	$88.85	$88.80
Purchase #4	$97.57	12.218%	$109.4911	$109.49	$109.50	$109.50
Purchase #5	$218.99	3.123%	$225.8291	$225.83	$225.85	$225.80
Purchase #6	$99.46	9.748%	$109.1554	$109.16	$109.15	$109.20
Purchase #7	$102.26	10.830%	$113.3348	$113.33	$113.35	$113.30
7 purchase totals =	$836.18		$900.3671	$900.37	$900.45	$900.30