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	$40.71	13.264%	$46.1098	$46.11	$46.10	$46.10
Purchase #2	$96.41	6.766%	$102.9331	$102.93	$102.95	$102.90
Purchase #3	$103.95	8.177%	$112.45	$112.45	$112.45	$112.50
Purchase #4	$94.34	5.806%	$99.8174	$99.82	$99.80	$99.80
Purchase #5	$165.72	6.417%	$176.3543	$176.35	$176.35	$176.40
Purchase #6	$110.48	11.732%	$123.4415	$123.44	$123.45	$123.40
Purchase #7	$66.56	10.162%	$73.3238	$73.32	$73.30	$73.30
7 purchase totals =	$678.17		$734.4299	$734.42	$734.40	$734.40