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	$156.29	11.340%	$174.0133	$174.01	$174.00	$174.00
Purchase #2	$157.42	6.179%	$167.147	$167.15	$167.15	$167.10
Purchase #3	$229.98	3.281%	$237.5256	$237.53	$237.55	$237.50
Purchase #4	$112.62	5.267%	$118.5517	$118.55	$118.55	$118.60
Purchase #5	$123.80	3.770%	$128.4673	$128.47	$128.45	$128.50
Purchase #6	$105.34	7.342%	$113.0741	$113.07	$113.05	$113.10
Purchase #7	$57.50	7.383%	$61.7452	$61.75	$61.75	$61.70
7 purchase totals =	$942.95		$1,000.5242	$1,000.53	$1,000.50	$1,000.50