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	$77.27	11.181%	$85.9096	$85.91	$85.90	$85.90
Purchase #2	$200.66	3.149%	$206.9788	$206.98	$207.00	$207.00
Purchase #3	$176.59	6.789%	$188.5787	$188.58	$188.60	$188.60
Purchase #4	$40.64	12.492%	$45.7167	$45.72	$45.70	$45.70
Purchase #5	$193.85	9.297%	$211.8722	$211.87	$211.85	$211.90
Purchase #6	$78.98	3.846%	$82.0176	$82.02	$82.00	$82.00
Purchase #7	$153.58	12.760%	$173.1768	$173.18	$173.20	$173.20
7 purchase totals =	$921.57		$994.2504	$994.26	$994.25	$994.30