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	$67.87	5.844%	$71.8363	$71.84	$71.85	$71.80
Purchase #2	$180.52	8.780%	$196.3697	$196.37	$196.35	$196.40
Purchase #3	$145.80	5.524%	$153.854	$153.85	$153.85	$153.90
Purchase #4	$226.45	9.832%	$248.7146	$248.71	$248.70	$248.70
Purchase #5	$75.86	7.443%	$81.5063	$81.51	$81.50	$81.50
Purchase #6	$77.59	10.195%	$85.5003	$85.50	$85.50	$85.50
Purchase #7	$211.58	6.702%	$225.7601	$225.76	$225.75	$225.80
7 purchase totals =	$985.67		$1,063.5413	$1,063.54	$1,063.50	$1,063.60