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	$104.25	7.382%	$111.9457	$111.95	$111.95	$111.90
Purchase #2	$173.53	13.112%	$196.2833	$196.28	$196.30	$196.30
Purchase #3	$198.66	7.133%	$212.8304	$212.83	$212.85	$212.80
Purchase #4	$190.93	4.177%	$198.9051	$198.91	$198.90	$198.90
Purchase #5	$50.65	4.323%	$52.8396	$52.84	$52.85	$52.80
Purchase #6	$92.40	10.437%	$102.0438	$102.04	$102.05	$102.00
Purchase #7	$84.79	5.354%	$89.3297	$89.33	$89.35	$89.30
7 purchase totals =	$895.21		$964.1776	$964.18	$964.25	$964.00