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	$80.88	3.569%	$83.7666	$83.77	$83.75	$83.80
Purchase #2	$56.66	4.549%	$59.2375	$59.24	$59.25	$59.20
Purchase #3	$49.73	9.159%	$54.2848	$54.28	$54.30	$54.30
Purchase #4	$150.67	5.226%	$158.544	$158.54	$158.55	$158.50
Purchase #5	$143.57	9.196%	$156.7727	$156.77	$156.75	$156.80
Purchase #6	$33.34	9.271%	$36.431	$36.43	$36.45	$36.40
Purchase #7	$111.97	11.788%	$125.169	$125.17	$125.15	$125.20
7 purchase totals =	$626.82		$674.2056	$674.20	$674.20	$674.20