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	$186.98	11.657%	$208.7763	$208.78	$208.80	$208.80
Purchase #2	$102.35	3.220%	$105.6457	$105.65	$105.65	$105.60
Purchase #3	$136.84	11.736%	$152.8995	$152.90	$152.90	$152.90
Purchase #4	$149.77	4.812%	$156.9769	$156.98	$157.00	$157.00
Purchase #5	$56.35	5.502%	$59.4504	$59.45	$59.45	$59.50
Purchase #6	$122.36	3.550%	$126.7038	$126.70	$126.70	$126.70
Purchase #7	$179.33	6.588%	$191.1443	$191.14	$191.15	$191.10
7 purchase totals =	$933.98		$1,001.5969	$1,001.60	$1,001.65	$1,001.60