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	$117.75	11.765%	$131.6033	$131.60	$131.60	$131.60
Purchase #2	$128.80	11.114%	$143.1148	$143.11	$143.10	$143.10
Purchase #3	$49.83	5.415%	$52.5283	$52.53	$52.55	$52.50
Purchase #4	$60.73	11.708%	$67.8403	$67.84	$67.85	$67.80
Purchase #5	$35.43	8.535%	$38.454	$38.45	$38.45	$38.50
Purchase #6	$51.60	6.230%	$54.8147	$54.81	$54.80	$54.80
Purchase #7	$182.67	6.686%	$194.8833	$194.88	$194.90	$194.90
7 purchase totals =	$626.81		$683.2387	$683.22	$683.25	$683.20