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	$130.38	11.534%	$145.418	$145.42	$145.40	$145.40
Purchase #2	$131.99	11.818%	$147.5886	$147.59	$147.60	$147.60
Purchase #3	$180.78	3.523%	$187.1489	$187.15	$187.15	$187.10
Purchase #4	$246.86	13.357%	$279.8331	$279.83	$279.85	$279.80
Purchase #5	$162.89	4.198%	$169.7281	$169.73	$169.75	$169.70
Purchase #6	$86.97	3.272%	$89.8157	$89.82	$89.80	$89.80
Purchase #7	$78.32	12.343%	$87.987	$87.99	$88.00	$88.00
7 purchase totals =	$1,018.19		$1,107.5194	$1,107.53	$1,107.55	$1,107.40