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	$56.29	9.557%	$61.6696	$61.67	$61.65	$61.70
Purchase #2	$156.67	13.831%	$178.339	$178.34	$178.35	$178.30
Purchase #3	$203.33	6.759%	$217.0731	$217.07	$217.05	$217.10
Purchase #4	$119.68	6.829%	$127.8529	$127.85	$127.85	$127.90
Purchase #5	$88.40	9.140%	$96.4798	$96.48	$96.50	$96.50
Purchase #6	$153.28	11.470%	$170.8612	$170.86	$170.85	$170.90
Purchase #7	$219.52	6.652%	$234.1225	$234.12	$234.10	$234.10
7 purchase totals =	$997.17		$1,086.3981	$1,086.39	$1,086.35	$1,086.50