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	$133.75	9.507%	$146.4656	$146.47	$146.45	$146.50
Purchase #2	$132.86	6.141%	$141.0189	$141.02	$141.00	$141.00
Purchase #3	$129.63	10.631%	$143.411	$143.41	$143.40	$143.40
Purchase #4	$55.95	11.661%	$62.4743	$62.47	$62.45	$62.50
Purchase #5	$10.72	3.133%	$11.0559	$11.06	$11.05	$11.10
Purchase #6	$209.56	4.657%	$219.3192	$219.32	$219.30	$219.30
Purchase #7	$118.31	7.737%	$127.4636	$127.46	$127.45	$127.50
7 purchase totals =	$790.78		$851.2085	$851.21	$851.10	$851.30