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	$191.43	11.143%	$212.761	$212.76	$212.75	$212.80
Purchase #2	$74.53	3.810%	$77.3696	$77.37	$77.35	$77.40
Purchase #3	$99.40	4.104%	$103.4794	$103.48	$103.50	$103.50
Purchase #4	$57.41	11.624%	$64.0833	$64.08	$64.10	$64.10
Purchase #5	$116.77	12.368%	$131.2121	$131.21	$131.20	$131.20
Purchase #6	$98.64	3.629%	$102.2196	$102.22	$102.20	$102.20
Purchase #7	$150.54	12.645%	$169.5758	$169.58	$169.60	$169.60
7 purchase totals =	$788.72		$860.7008	$860.70	$860.70	$860.80