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	$97.67	10.259%	$107.69	$107.69	$107.70	$107.70
Purchase #2	$50.58	10.514%	$55.898	$55.90	$55.90	$55.90
Purchase #3	$171.92	5.197%	$180.8547	$180.85	$180.85	$180.90
Purchase #4	$217.47	3.604%	$225.3076	$225.31	$225.30	$225.30
Purchase #5	$173.78	13.231%	$196.7728	$196.77	$196.75	$196.80
Purchase #6	$115.76	4.299%	$120.7365	$120.74	$120.75	$120.70
Purchase #7	$111.64	6.844%	$119.2806	$119.28	$119.30	$119.30
7 purchase totals =	$938.82		$1,006.5402	$1,006.54	$1,006.55	$1,006.60