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	$61.87	11.349%	$68.8916	$68.89	$68.90	$68.90
Purchase #2	$41.75	5.653%	$44.1101	$44.11	$44.10	$44.10
Purchase #3	$67.92	5.814%	$71.8689	$71.87	$71.85	$71.90
Purchase #4	$33.81	4.185%	$35.2249	$35.22	$35.20	$35.20
Purchase #5	$59.49	8.792%	$64.7204	$64.72	$64.70	$64.70
Purchase #6	$53.29	5.147%	$56.0328	$56.03	$56.05	$56.00
Purchase #7	$148.70	13.357%	$168.5619	$168.56	$168.55	$168.60
7 purchase totals =	$466.83		$509.4106	$509.40	$509.35	$509.40