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	$80.70	6.520%	$85.9616	$85.96	$85.95	$86.00
Purchase #2	$105.49	6.342%	$112.1802	$112.18	$112.20	$112.20
Purchase #3	$38.76	12.731%	$43.6945	$43.69	$43.70	$43.70
Purchase #4	$126.44	10.512%	$139.7314	$139.73	$139.75	$139.70
Purchase #5	$67.41	7.147%	$72.2278	$72.23	$72.25	$72.20
Purchase #6	$134.74	6.597%	$143.6288	$143.63	$143.65	$143.60
Purchase #7	$151.53	5.427%	$159.7535	$159.75	$159.75	$159.80
7 purchase totals =	$705.07		$757.1778	$757.17	$757.25	$757.20