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	$122.64	9.367%	$134.1277	$134.13	$134.15	$134.10
Purchase #2	$119.59	9.466%	$130.9104	$130.91	$130.90	$130.90
Purchase #3	$200.76	7.861%	$216.5417	$216.54	$216.55	$216.50
Purchase #4	$181.37	10.272%	$200.0003	$200.00	$200.00	$200.00
Purchase #5	$80.37	11.213%	$89.3819	$89.38	$89.40	$89.40
Purchase #6	$230.86	10.426%	$254.9295	$254.93	$254.95	$254.90
Purchase #7	$68.93	10.400%	$76.0987	$76.10	$76.10	$76.10
7 purchase totals =	$1,004.52		$1,101.9902	$1,101.99	$1,102.05	$1,101.90