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	$95.94	11.773%	$107.235	$107.24	$107.25	$107.20
Purchase #2	$143.33	6.658%	$152.8729	$152.87	$152.85	$152.90
Purchase #3	$102.49	4.851%	$107.4618	$107.46	$107.45	$107.50
Purchase #4	$18.58	4.864%	$19.4837	$19.48	$19.50	$19.50
Purchase #5	$183.51	3.818%	$190.5164	$190.52	$190.50	$190.50
Purchase #6	$213.46	6.840%	$228.0607	$228.06	$228.05	$228.10
Purchase #7	$88.43	7.712%	$95.2497	$95.25	$95.25	$95.20
7 purchase totals =	$845.74		$900.8802	$900.88	$900.85	$900.90