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	$93.43	7.701%	$100.625	$100.63	$100.65	$100.60
Purchase #2	$80.93	11.741%	$90.432	$90.43	$90.45	$90.40
Purchase #3	$49.76	8.726%	$54.1021	$54.10	$54.10	$54.10
Purchase #4	$11.57	3.669%	$11.9945	$11.99	$12.00	$12.00
Purchase #5	$81.76	3.296%	$84.4548	$84.45	$84.45	$84.50
Purchase #6	$234.32	13.414%	$265.7517	$265.75	$265.75	$265.80
Purchase #7	$147.54	5.111%	$155.0808	$155.08	$155.10	$155.10
7 purchase totals =	$699.31		$762.4409	$762.43	$762.50	$762.50