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	$7.52	5.516%	$7.9348	$7.93	$7.95	$7.90
Purchase #2	$197.47	10.445%	$218.0957	$218.10	$218.10	$218.10
Purchase #3	$38.33	9.792%	$42.0833	$42.08	$42.10	$42.10
Purchase #4	$31.54	6.726%	$33.6614	$33.66	$33.65	$33.70
Purchase #5	$247.59	4.413%	$258.5161	$258.52	$258.50	$258.50
Purchase #6	$91.95	10.429%	$101.5395	$101.54	$101.55	$101.50
Purchase #7	$168.39	9.208%	$183.8954	$183.90	$183.90	$183.90
7 purchase totals =	$782.79		$845.7262	$845.73	$845.75	$845.70