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	$96.54	13.785%	$109.848	$109.85	$109.85	$109.80
Purchase #2	$99.46	3.609%	$103.0495	$103.05	$103.05	$103.00
Purchase #3	$173.28	13.477%	$196.6329	$196.63	$196.65	$196.60
Purchase #4	$173.53	10.465%	$191.6899	$191.69	$191.70	$191.70
Purchase #5	$246.94	9.291%	$269.8832	$269.88	$269.90	$269.90
Purchase #6	$161.79	4.228%	$168.6305	$168.63	$168.65	$168.60
Purchase #7	$45.57	8.203%	$49.3081	$49.31	$49.30	$49.30
7 purchase totals =	$997.11		$1,089.0421	$1,089.04	$1,089.10	$1,088.90