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	$79.42	5.454%	$83.7516	$83.75	$83.75	$83.80
Purchase #2	$108.97	13.655%	$123.8499	$123.85	$123.85	$123.80
Purchase #3	$157.72	6.196%	$167.4923	$167.49	$167.50	$167.50
Purchase #4	$95.65	3.217%	$98.7271	$98.73	$98.75	$98.70
Purchase #5	$222.62	7.308%	$238.8891	$238.89	$238.90	$238.90
Purchase #6	$75.33	7.673%	$81.1101	$81.11	$81.10	$81.10
Purchase #7	$169.78	3.432%	$175.6068	$175.61	$175.60	$175.60
7 purchase totals =	$909.49		$969.4269	$969.43	$969.45	$969.40