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	$109.96	11.638%	$122.7571	$122.76	$122.75	$122.80
Purchase #2	$188.83	12.411%	$212.2657	$212.27	$212.25	$212.30
Purchase #3	$74.62	5.281%	$78.5607	$78.56	$78.55	$78.60
Purchase #4	$171.30	4.791%	$179.507	$179.51	$179.50	$179.50
Purchase #5	$54.84	7.672%	$59.0473	$59.05	$59.05	$59.00
Purchase #6	$122.42	12.119%	$137.2561	$137.26	$137.25	$137.30
Purchase #7	$242.56	9.573%	$265.7803	$265.78	$265.80	$265.80
7 purchase totals =	$964.53		$1,055.1742	$1,055.19	$1,055.15	$1,055.30