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	$59.66	7.830%	$64.3314	$64.33	$64.35	$64.30
Purchase #2	$67.54	6.349%	$71.8281	$71.83	$71.85	$71.80
Purchase #3	$33.88	10.328%	$37.3791	$37.38	$37.40	$37.40
Purchase #4	$197.89	3.359%	$204.5371	$204.54	$204.55	$204.50
Purchase #5	$224.37	13.167%	$253.9128	$253.91	$253.90	$253.90
Purchase #6	$45.31	4.174%	$47.2012	$47.20	$47.20	$47.20
Purchase #7	$158.67	13.187%	$179.5938	$179.59	$179.60	$179.60
7 purchase totals =	$787.32		$858.7835	$858.78	$858.85	$858.70