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	$21.32	5.106%	$22.4086	$22.41	$22.40	$22.40
Purchase #2	$89.27	11.410%	$99.4557	$99.46	$99.45	$99.50
Purchase #3	$62.47	11.867%	$69.8833	$69.88	$69.90	$69.90
Purchase #4	$91.43	8.398%	$99.1083	$99.11	$99.10	$99.10
Purchase #5	$125.81	12.861%	$141.9904	$141.99	$142.00	$142.00
Purchase #6	$249.47	12.515%	$280.6912	$280.69	$280.70	$280.70
Purchase #7	$158.70	8.556%	$172.2784	$172.28	$172.30	$172.30
7 purchase totals =	$798.47		$885.8159	$885.82	$885.85	$885.90