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	$82.80	5.121%	$87.0402	$87.04	$87.05	$87.00
Purchase #2	$146.32	6.176%	$155.3567	$155.36	$155.35	$155.40
Purchase #3	$169.49	3.152%	$174.8323	$174.83	$174.85	$174.80
Purchase #4	$37.64	7.651%	$40.5198	$40.52	$40.50	$40.50
Purchase #5	$202.47	9.352%	$221.405	$221.41	$221.40	$221.40
Purchase #6	$44.84	4.844%	$47.012	$47.01	$47.00	$47.00
Purchase #7	$153.29	12.133%	$171.8887	$171.89	$171.90	$171.90
7 purchase totals =	$836.85		$898.0547	$898.06	$898.05	$898.00