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	$136.71	3.501%	$141.4962	$141.50	$141.50	$141.50
Purchase #2	$127.63	11.465%	$142.2628	$142.26	$142.25	$142.30
Purchase #3	$65.51	8.466%	$71.0561	$71.06	$71.05	$71.10
Purchase #4	$113.71	5.335%	$119.7764	$119.78	$119.80	$119.80
Purchase #5	$211.30	8.256%	$228.7449	$228.74	$228.75	$228.70
Purchase #6	$244.27	4.387%	$254.9861	$254.99	$255.00	$255.00
Purchase #7	$114.63	7.341%	$123.045	$123.05	$123.05	$123.00
7 purchase totals =	$1,013.76		$1,081.3675	$1,081.38	$1,081.40	$1,081.40