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	$218.44	11.457%	$243.4667	$243.47	$243.45	$243.50
Purchase #2	$49.81	11.244%	$55.4106	$55.41	$55.40	$55.40
Purchase #3	$193.95	7.272%	$208.054	$208.05	$208.05	$208.10
Purchase #4	$152.53	12.300%	$171.2912	$171.29	$171.30	$171.30
Purchase #5	$248.80	12.333%	$279.4845	$279.48	$279.50	$279.50
Purchase #6	$102.92	6.333%	$109.4379	$109.44	$109.45	$109.40
Purchase #7	$76.63	13.431%	$86.9222	$86.92	$86.90	$86.90
7 purchase totals =	$1,043.08		$1,154.0671	$1,154.06	$1,154.05	$1,154.10