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	$48.54	8.516%	$52.6737	$52.67	$52.65	$52.70
Purchase #2	$64.93	13.812%	$73.8981	$73.90	$73.90	$73.90
Purchase #3	$174.25	12.805%	$196.5627	$196.56	$196.55	$196.60
Purchase #4	$131.71	5.726%	$139.2517	$139.25	$139.25	$139.30
Purchase #5	$164.26	7.428%	$176.4612	$176.46	$176.45	$176.50
Purchase #6	$67.56	13.833%	$76.9056	$76.91	$76.90	$76.90
Purchase #7	$197.53	7.736%	$212.8109	$212.81	$212.80	$212.80
7 purchase totals =	$848.78		$928.5639	$928.56	$928.50	$928.70