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	$62.70	5.495%	$66.1454	$66.15	$66.15	$66.10
Purchase #2	$198.53	6.649%	$211.7303	$211.73	$211.75	$211.70
Purchase #3	$159.40	5.323%	$167.8849	$167.88	$167.90	$167.90
Purchase #4	$189.40	4.842%	$198.5707	$198.57	$198.55	$198.60
Purchase #5	$165.27	10.355%	$182.3837	$182.38	$182.40	$182.40
Purchase #6	$136.60	12.688%	$153.9318	$153.93	$153.95	$153.90
Purchase #7	$12.36	12.589%	$13.916	$13.92	$13.90	$13.90
7 purchase totals =	$924.26		$994.5628	$994.56	$994.60	$994.50