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	$179.34	3.361%	$185.3676	$185.37	$185.35	$185.40
Purchase #2	$186.62	13.787%	$212.3493	$212.35	$212.35	$212.30
Purchase #3	$105.50	5.780%	$111.5979	$111.60	$111.60	$111.60
Purchase #4	$231.25	10.482%	$255.4896	$255.49	$255.50	$255.50
Purchase #5	$113.90	5.834%	$120.5449	$120.54	$120.55	$120.50
Purchase #6	$92.97	5.675%	$98.246	$98.25	$98.25	$98.20
Purchase #7	$170.57	12.247%	$191.4597	$191.46	$191.45	$191.50
7 purchase totals =	$1,080.15		$1,175.0550	$1,175.06	$1,175.05	$1,175.00