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	$45.28	5.398%	$47.7242	$47.72	$47.70	$47.70
Purchase #2	$61.78	7.811%	$66.6056	$66.61	$66.60	$66.60
Purchase #3	$150.26	4.304%	$156.7272	$156.73	$156.75	$156.70
Purchase #4	$161.37	12.328%	$181.2637	$181.26	$181.25	$181.30
Purchase #5	$154.86	4.556%	$161.9154	$161.92	$161.90	$161.90
Purchase #6	$210.47	5.615%	$222.2879	$222.29	$222.30	$222.30
Purchase #7	$227.52	3.430%	$235.3239	$235.32	$235.30	$235.30
7 purchase totals =	$1,011.54		$1,071.8479	$1,071.85	$1,071.80	$1,071.80