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	$47.57	13.133%	$53.8174	$53.82	$53.80	$53.80
Purchase #2	$53.27	11.756%	$59.5324	$59.53	$59.55	$59.50
Purchase #3	$238.85	3.860%	$248.0696	$248.07	$248.05	$248.10
Purchase #4	$55.34	13.697%	$62.9199	$62.92	$62.90	$62.90
Purchase #5	$128.41	11.210%	$142.8048	$142.80	$142.80	$142.80
Purchase #6	$18.34	11.405%	$20.4317	$20.43	$20.45	$20.40
Purchase #7	$165.69	3.470%	$171.4394	$171.44	$171.45	$171.40
7 purchase totals =	$707.47		$759.0152	$759.01	$759.00	$758.90