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	$142.59	6.760%	$152.2291	$152.23	$152.25	$152.20
Purchase #2	$121.50	4.774%	$127.3004	$127.30	$127.30	$127.30
Purchase #3	$200.58	5.619%	$211.8506	$211.85	$211.85	$211.90
Purchase #4	$200.61	9.545%	$219.7582	$219.76	$219.75	$219.80
Purchase #5	$54.70	13.571%	$62.1233	$62.12	$62.10	$62.10
Purchase #6	$40.94	6.407%	$43.563	$43.56	$43.55	$43.60
Purchase #7	$130.77	9.404%	$143.0676	$143.07	$143.05	$143.10
7 purchase totals =	$891.69		$959.8922	$959.89	$959.85	$960.00