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	$104.57	5.182%	$109.9888	$109.99	$110.00	$110.00
Purchase #2	$43.43	7.352%	$46.623	$46.62	$46.60	$46.60
Purchase #3	$240.43	6.782%	$256.736	$256.74	$256.75	$256.70
Purchase #4	$98.80	3.853%	$102.6068	$102.61	$102.60	$102.60
Purchase #5	$100.26	5.332%	$105.6059	$105.61	$105.60	$105.60
Purchase #6	$94.88	10.606%	$104.943	$104.94	$104.95	$104.90
Purchase #7	$59.60	12.438%	$67.013	$67.01	$67.00	$67.00
7 purchase totals =	$741.97		$793.5165	$793.52	$793.50	$793.40