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	$179.76	6.540%	$191.5163	$191.52	$191.50	$191.50
Purchase #2	$143.95	7.585%	$154.8686	$154.87	$154.85	$154.90
Purchase #3	$163.48	11.170%	$181.7407	$181.74	$181.75	$181.70
Purchase #4	$158.59	12.208%	$177.9507	$177.95	$177.95	$178.00
Purchase #5	$59.32	8.273%	$64.2275	$64.23	$64.25	$64.20
Purchase #6	$249.59	5.599%	$263.5645	$263.56	$263.55	$263.60
Purchase #7	$29.46	13.755%	$33.5122	$33.51	$33.50	$33.50
7 purchase totals =	$984.15		$1,067.3805	$1,067.38	$1,067.35	$1,067.40