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	$207.71	4.127%	$216.2822	$216.28	$216.30	$216.30
Purchase #2	$67.99	6.560%	$72.4501	$72.45	$72.45	$72.50
Purchase #3	$240.79	5.563%	$254.1851	$254.19	$254.20	$254.20
Purchase #4	$186.27	10.169%	$205.2118	$205.21	$205.20	$205.20
Purchase #5	$77.28	13.275%	$87.5389	$87.54	$87.55	$87.50
Purchase #6	$77.81	11.741%	$86.9457	$86.95	$86.95	$86.90
Purchase #7	$72.95	13.612%	$82.88	$82.88	$82.90	$82.90
7 purchase totals =	$930.80		$1,005.4938	$1,005.50	$1,005.55	$1,005.50