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	$56.42	5.170%	$59.3369	$59.34	$59.35	$59.30
Purchase #2	$143.83	4.485%	$150.2808	$150.28	$150.30	$150.30
Purchase #3	$202.33	9.845%	$222.2494	$222.25	$222.25	$222.20
Purchase #4	$193.30	5.820%	$204.5501	$204.55	$204.55	$204.60
Purchase #5	$213.50	4.190%	$222.4457	$222.45	$222.45	$222.40
Purchase #6	$165.94	6.125%	$176.1038	$176.10	$176.10	$176.10
Purchase #7	$97.82	3.695%	$101.4344	$101.43	$101.45	$101.40
7 purchase totals =	$1,073.14		$1,136.4011	$1,136.40	$1,136.45	$1,136.30