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	$36.69	3.411%	$37.9415	$37.94	$37.95	$37.90
Purchase #2	$229.32	8.864%	$249.6469	$249.65	$249.65	$249.60
Purchase #3	$177.50	11.713%	$198.2906	$198.29	$198.30	$198.30
Purchase #4	$55.54	7.759%	$59.8493	$59.85	$59.85	$59.80
Purchase #5	$126.59	6.554%	$134.8867	$134.89	$134.90	$134.90
Purchase #6	$222.81	4.723%	$233.3333	$233.33	$233.35	$233.30
Purchase #7	$227.28	13.801%	$258.6469	$258.65	$258.65	$258.60
7 purchase totals =	$1,075.73		$1,172.5952	$1,172.60	$1,172.65	$1,172.40