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	$235.75	12.535%	$265.3013	$265.30	$265.30	$265.30
Purchase #2	$141.93	8.227%	$153.6066	$153.61	$153.60	$153.60
Purchase #3	$125.41	12.801%	$141.4637	$141.46	$141.45	$141.50
Purchase #4	$73.51	12.777%	$82.9024	$82.90	$82.90	$82.90
Purchase #5	$149.38	5.780%	$158.0142	$158.01	$158.00	$158.00
Purchase #6	$98.45	4.760%	$103.1362	$103.14	$103.15	$103.10
Purchase #7	$100.26	8.656%	$108.9385	$108.94	$108.95	$108.90
7 purchase totals =	$924.69		$1,013.3629	$1,013.36	$1,013.35	$1,013.30