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	$73.82	4.440%	$77.0976	$77.10	$77.10	$77.10
Purchase #2	$67.74	5.568%	$71.5118	$71.51	$71.50	$71.50
Purchase #3	$13.88	8.334%	$15.0368	$15.04	$15.05	$15.00
Purchase #4	$211.62	10.506%	$233.8528	$233.85	$233.85	$233.90
Purchase #5	$119.86	8.742%	$130.3382	$130.34	$130.35	$130.30
Purchase #6	$160.39	5.512%	$169.2307	$169.23	$169.25	$169.20
Purchase #7	$42.38	6.744%	$45.2381	$45.24	$45.25	$45.20
7 purchase totals =	$689.69		$742.3060	$742.31	$742.35	$742.20