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	$32.70	8.416%	$35.452	$35.45	$35.45	$35.50
Purchase #2	$108.33	3.383%	$111.9948	$111.99	$112.00	$112.00
Purchase #3	$29.75	12.620%	$33.5045	$33.50	$33.50	$33.50
Purchase #4	$36.43	9.230%	$39.7925	$39.79	$39.80	$39.80
Purchase #5	$229.54	10.540%	$253.7335	$253.73	$253.75	$253.70
Purchase #6	$191.88	4.693%	$200.8849	$200.88	$200.90	$200.90
Purchase #7	$102.58	6.533%	$109.2816	$109.28	$109.30	$109.30
7 purchase totals =	$731.21		$784.6438	$784.62	$784.70	$784.70