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	$172.73	8.623%	$187.6245	$187.62	$187.60	$187.60
Purchase #2	$111.89	3.299%	$115.5813	$115.58	$115.60	$115.60
Purchase #3	$54.34	9.523%	$59.5148	$59.51	$59.50	$59.50
Purchase #4	$92.85	7.765%	$100.0598	$100.06	$100.05	$100.10
Purchase #5	$195.50	11.431%	$217.8476	$217.85	$217.85	$217.80
Purchase #6	$221.96	11.853%	$248.2689	$248.27	$248.25	$248.30
Purchase #7	$103.93	7.336%	$111.5543	$111.55	$111.55	$111.60
7 purchase totals =	$953.20		$1,040.4512	$1,040.44	$1,040.40	$1,040.50