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	$144.52	7.629%	$155.5454	$155.55	$155.55	$155.50
Purchase #2	$215.51	3.132%	$222.2598	$222.26	$222.25	$222.30
Purchase #3	$20.64	5.171%	$21.7073	$21.71	$21.70	$21.70
Purchase #4	$169.34	7.796%	$182.5417	$182.54	$182.55	$182.50
Purchase #5	$194.30	13.483%	$220.4975	$220.50	$220.50	$220.50
Purchase #6	$92.36	6.418%	$98.2877	$98.29	$98.30	$98.30
Purchase #7	$235.75	5.864%	$249.5744	$249.57	$249.55	$249.60
7 purchase totals =	$1,072.42		$1,150.4138	$1,150.42	$1,150.40	$1,150.40