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	$78.35	8.629%	$85.1108	$85.11	$85.10	$85.10
Purchase #2	$134.47	13.625%	$152.7915	$152.79	$152.80	$152.80
Purchase #3	$181.29	8.355%	$196.4368	$196.44	$196.45	$196.40
Purchase #4	$179.50	5.173%	$188.7855	$188.79	$188.80	$188.80
Purchase #5	$80.46	6.214%	$85.4598	$85.46	$85.45	$85.50
Purchase #6	$97.65	8.761%	$106.2051	$106.21	$106.20	$106.20
Purchase #7	$206.67	3.475%	$213.8518	$213.85	$213.85	$213.90
7 purchase totals =	$958.39		$1,028.6413	$1,028.65	$1,028.65	$1,028.70