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	$195.38	8.735%	$212.4464	$212.45	$212.45	$212.40
Purchase #2	$200.88	4.440%	$209.7991	$209.80	$209.80	$209.80
Purchase #3	$58.43	8.626%	$63.4702	$63.47	$63.45	$63.50
Purchase #4	$80.71	6.720%	$86.1337	$86.13	$86.15	$86.10
Purchase #5	$154.90	9.422%	$169.4947	$169.49	$169.50	$169.50
Purchase #6	$179.69	9.481%	$196.7264	$196.73	$196.75	$196.70
Purchase #7	$30.46	9.575%	$33.3765	$33.38	$33.40	$33.40
7 purchase totals =	$900.45		$971.4470	$971.45	$971.50	$971.40