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	$244.47	7.593%	$263.0326	$263.03	$263.05	$263.00
Purchase #2	$99.61	12.302%	$111.864	$111.86	$111.85	$111.90
Purchase #3	$233.89	10.208%	$257.7655	$257.77	$257.75	$257.80
Purchase #4	$92.53	10.514%	$102.2586	$102.26	$102.25	$102.30
Purchase #5	$53.46	11.789%	$59.7624	$59.76	$59.75	$59.80
Purchase #6	$233.78	10.800%	$259.0282	$259.03	$259.05	$259.00
Purchase #7	$50.58	9.330%	$55.2991	$55.30	$55.30	$55.30
7 purchase totals =	$1,008.32		$1,109.0104	$1,109.01	$1,109.00	$1,109.10