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	$182.67	4.788%	$191.4162	$191.42	$191.40	$191.40
Purchase #2	$94.92	5.873%	$100.4947	$100.49	$100.50	$100.50
Purchase #3	$77.62	10.787%	$85.9929	$85.99	$86.00	$86.00
Purchase #4	$130.28	5.450%	$137.3803	$137.38	$137.40	$137.40
Purchase #5	$174.77	6.179%	$185.569	$185.57	$185.55	$185.60
Purchase #6	$34.37	8.824%	$37.4028	$37.40	$37.40	$37.40
Purchase #7	$80.42	9.410%	$87.9875	$87.99	$88.00	$88.00
7 purchase totals =	$775.05		$826.2434	$826.24	$826.25	$826.30