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	$53.41	5.674%	$56.4405	$56.44	$56.45	$56.40
Purchase #2	$67.36	6.622%	$71.8206	$71.82	$71.80	$71.80
Purchase #3	$15.96	3.727%	$16.5548	$16.55	$16.55	$16.60
Purchase #4	$218.38	7.847%	$235.5163	$235.52	$235.50	$235.50
Purchase #5	$82.53	13.244%	$93.4603	$93.46	$93.45	$93.50
Purchase #6	$24.89	12.422%	$27.9818	$27.98	$28.00	$28.00
Purchase #7	$57.32	4.527%	$59.9149	$59.91	$59.90	$59.90
7 purchase totals =	$519.85		$561.6892	$561.68	$561.65	$561.70