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	$249.71	5.294%	$262.9296	$262.93	$262.95	$262.90
Purchase #2	$111.76	6.273%	$118.7707	$118.77	$118.75	$118.80
Purchase #3	$202.27	9.546%	$221.5787	$221.58	$221.60	$221.60
Purchase #4	$171.85	7.365%	$184.5068	$184.51	$184.50	$184.50
Purchase #5	$126.91	7.355%	$136.2442	$136.24	$136.25	$136.20
Purchase #6	$80.39	6.150%	$85.334	$85.33	$85.35	$85.30
Purchase #7	$179.31	6.646%	$191.2269	$191.23	$191.25	$191.20
7 purchase totals =	$1,122.20		$1,200.5909	$1,200.59	$1,200.65	$1,200.50