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	$65.31	9.236%	$71.342	$71.34	$71.35	$71.30
Purchase #2	$134.26	7.377%	$144.1644	$144.16	$144.15	$144.20
Purchase #3	$73.63	6.798%	$78.6354	$78.64	$78.65	$78.60
Purchase #4	$67.91	9.402%	$74.2949	$74.29	$74.30	$74.30
Purchase #5	$162.73	10.821%	$180.339	$180.34	$180.35	$180.30
Purchase #6	$176.28	7.172%	$188.9228	$188.92	$188.90	$188.90
Purchase #7	$19.59	5.214%	$20.6114	$20.61	$20.60	$20.60
7 purchase totals =	$699.71		$758.3099	$758.30	$758.30	$758.20