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	$143.25	9.582%	$156.9762	$156.98	$157.00	$157.00
Purchase #2	$148.83	12.194%	$166.9783	$166.98	$167.00	$167.00
Purchase #3	$214.96	6.322%	$228.5498	$228.55	$228.55	$228.50
Purchase #4	$98.45	11.363%	$109.6369	$109.64	$109.65	$109.60
Purchase #5	$32.97	12.730%	$37.1671	$37.17	$37.15	$37.20
Purchase #6	$180.95	8.563%	$196.4447	$196.44	$196.45	$196.40
Purchase #7	$95.38	4.108%	$99.2982	$99.30	$99.30	$99.30
7 purchase totals =	$914.79		$995.0512	$995.06	$995.10	$995.00