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	$101.46	8.375%	$109.9573	$109.96	$109.95	$110.00
Purchase #2	$102.46	3.362%	$105.9047	$105.90	$105.90	$105.90
Purchase #3	$65.47	13.716%	$74.4499	$74.45	$74.45	$74.40
Purchase #4	$114.80	8.481%	$124.5362	$124.54	$124.55	$124.50
Purchase #5	$191.67	7.619%	$206.2733	$206.27	$206.25	$206.30
Purchase #6	$96.54	9.222%	$105.4429	$105.44	$105.45	$105.40
Purchase #7	$174.64	4.111%	$181.8195	$181.82	$181.80	$181.80
7 purchase totals =	$847.04		$908.3838	$908.38	$908.35	$908.30