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	$202.35	13.582%	$229.8332	$229.83	$229.85	$229.80
Purchase #2	$170.57	6.689%	$181.9794	$181.98	$182.00	$182.00
Purchase #3	$166.99	13.144%	$188.9392	$188.94	$188.95	$188.90
Purchase #4	$56.73	4.788%	$59.4462	$59.45	$59.45	$59.40
Purchase #5	$45.93	9.764%	$50.4146	$50.41	$50.40	$50.40
Purchase #6	$30.49	5.584%	$32.1926	$32.19	$32.20	$32.20
Purchase #7	$232.76	12.786%	$262.5207	$262.52	$262.50	$262.50
7 purchase totals =	$905.82		$1,005.3259	$1,005.32	$1,005.35	$1,005.20