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	$104.74	4.564%	$109.5203	$109.52	$109.50	$109.50
Purchase #2	$46.79	6.738%	$49.9427	$49.94	$49.95	$49.90
Purchase #3	$170.36	3.628%	$176.5407	$176.54	$176.55	$176.50
Purchase #4	$17.89	5.815%	$18.9303	$18.93	$18.95	$18.90
Purchase #5	$148.53	12.404%	$166.9537	$166.95	$166.95	$167.00
Purchase #6	$88.65	6.335%	$94.266	$94.27	$94.25	$94.30
Purchase #7	$208.58	4.647%	$218.2727	$218.27	$218.25	$218.30
7 purchase totals =	$785.54		$834.4264	$834.42	$834.40	$834.40