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	$80.75	5.572%	$85.2494	$85.25	$85.25	$85.20
Purchase #2	$30.76	7.360%	$33.0239	$33.02	$33.00	$33.00
Purchase #3	$208.27	4.715%	$218.0899	$218.09	$218.10	$218.10
Purchase #4	$103.54	8.372%	$112.2084	$112.21	$112.20	$112.20
Purchase #5	$170.59	9.864%	$187.417	$187.42	$187.40	$187.40
Purchase #6	$92.42	3.394%	$95.5567	$95.56	$95.55	$95.60
Purchase #7	$238.61	4.724%	$249.8819	$249.88	$249.90	$249.90
7 purchase totals =	$924.94		$981.4272	$981.43	$981.40	$981.40