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	$163.55	13.732%	$186.0087	$186.01	$186.00	$186.00
Purchase #2	$146.54	11.111%	$162.8221	$162.82	$162.80	$162.80
Purchase #3	$57.87	7.599%	$62.2675	$62.27	$62.25	$62.30
Purchase #4	$187.98	5.443%	$198.2118	$198.21	$198.20	$198.20
Purchase #5	$185.74	4.130%	$193.4111	$193.41	$193.40	$193.40
Purchase #6	$95.25	10.794%	$105.5313	$105.53	$105.55	$105.50
Purchase #7	$119.58	7.436%	$128.472	$128.47	$128.45	$128.50
7 purchase totals =	$956.51		$1,036.7245	$1,036.72	$1,036.65	$1,036.70