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	$73.25	13.636%	$83.2384	$83.24	$83.25	$83.20
Purchase #2	$183.66	6.773%	$196.0993	$196.10	$196.10	$196.10
Purchase #3	$99.86	13.102%	$112.9437	$112.94	$112.95	$112.90
Purchase #4	$156.53	8.730%	$170.1951	$170.20	$170.20	$170.20
Purchase #5	$208.93	6.107%	$221.6894	$221.69	$221.70	$221.70
Purchase #6	$70.85	12.794%	$79.9145	$79.91	$79.90	$79.90
Purchase #7	$136.64	13.816%	$155.5182	$155.52	$155.50	$155.50
7 purchase totals =	$929.72		$1,019.5986	$1,019.60	$1,019.60	$1,019.50