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	$243.54	5.824%	$257.7238	$257.72	$257.70	$257.70
Purchase #2	$47.37	13.615%	$53.8194	$53.82	$53.80	$53.80
Purchase #3	$177.36	9.543%	$194.2855	$194.29	$194.30	$194.30
Purchase #4	$238.43	6.627%	$254.2308	$254.23	$254.25	$254.20
Purchase #5	$167.35	8.459%	$181.5061	$181.51	$181.50	$181.50
Purchase #6	$66.68	8.354%	$72.2504	$72.25	$72.25	$72.30
Purchase #7	$175.30	6.279%	$186.3071	$186.31	$186.30	$186.30
7 purchase totals =	$1,116.03		$1,200.1231	$1,200.13	$1,200.10	$1,200.10