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	$142.97	6.735%	$152.599	$152.60	$152.60	$152.60
Purchase #2	$78.84	13.702%	$89.6427	$89.64	$89.65	$89.60
Purchase #3	$43.99	4.569%	$45.9999	$46.00	$46.00	$46.00
Purchase #4	$80.85	10.382%	$89.2438	$89.24	$89.25	$89.20
Purchase #5	$221.54	5.767%	$234.3162	$234.32	$234.30	$234.30
Purchase #6	$35.47	5.794%	$37.5251	$37.53	$37.55	$37.50
Purchase #7	$83.93	9.760%	$92.1216	$92.12	$92.10	$92.10
7 purchase totals =	$687.59		$741.4483	$741.45	$741.45	$741.30