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	$122.27	9.814%	$134.2696	$134.27	$134.25	$134.30
Purchase #2	$174.40	9.485%	$190.9418	$190.94	$190.95	$190.90
Purchase #3	$198.90	7.834%	$214.4818	$214.48	$214.50	$214.50
Purchase #4	$234.30	13.416%	$265.7337	$265.73	$265.75	$265.70
Purchase #5	$12.84	13.816%	$14.614	$14.61	$14.60	$14.60
Purchase #6	$55.62	7.519%	$59.8021	$59.80	$59.80	$59.80
Purchase #7	$157.40	12.374%	$176.8767	$176.88	$176.90	$176.90
7 purchase totals =	$955.73		$1,056.7197	$1,056.71	$1,056.75	$1,056.70