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	$115.66	10.336%	$127.6146	$127.61	$127.60	$127.60
Purchase #2	$10.45	13.701%	$11.8818	$11.88	$11.90	$11.90
Purchase #3	$131.92	12.668%	$148.6316	$148.63	$148.65	$148.60
Purchase #4	$63.87	11.761%	$71.3818	$71.38	$71.40	$71.40
Purchase #5	$150.89	13.489%	$171.2436	$171.24	$171.25	$171.20
Purchase #6	$183.77	9.126%	$200.5409	$200.54	$200.55	$200.50
Purchase #7	$122.96	13.811%	$139.942	$139.94	$139.95	$139.90
7 purchase totals =	$779.52		$871.2363	$871.22	$871.30	$871.10