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	$79.63	8.679%	$86.5411	$86.54	$86.55	$86.50
Purchase #2	$17.33	5.190%	$18.2294	$18.23	$18.25	$18.20
Purchase #3	$143.90	5.838%	$152.3009	$152.30	$152.30	$152.30
Purchase #4	$58.27	6.235%	$61.9031	$61.90	$61.90	$61.90
Purchase #5	$109.52	3.167%	$112.9885	$112.99	$113.00	$113.00
Purchase #6	$147.27	6.165%	$156.3492	$156.35	$156.35	$156.30
Purchase #7	$81.40	10.110%	$89.6295	$89.63	$89.65	$89.60
7 purchase totals =	$637.32		$677.9417	$677.94	$678.00	$677.80