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	$76.78	12.696%	$86.528	$86.53	$86.55	$86.50
Purchase #2	$178.86	12.672%	$201.5251	$201.53	$201.55	$201.50
Purchase #3	$66.26	7.397%	$71.1613	$71.16	$71.15	$71.20
Purchase #4	$214.96	3.599%	$222.6964	$222.70	$222.70	$222.70
Purchase #5	$208.36	12.159%	$233.6945	$233.69	$233.70	$233.70
Purchase #6	$64.88	3.810%	$67.3519	$67.35	$67.35	$67.40
Purchase #7	$171.29	4.514%	$179.022	$179.02	$179.00	$179.00
7 purchase totals =	$981.39		$1,061.9792	$1,061.98	$1,062.00	$1,062.00