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	$67.53	11.641%	$75.3912	$75.39	$75.40	$75.40
Purchase #2	$237.89	13.667%	$270.4024	$270.40	$270.40	$270.40
Purchase #3	$71.82	12.522%	$80.8133	$80.81	$80.80	$80.80
Purchase #4	$176.32	7.305%	$189.2002	$189.20	$189.20	$189.20
Purchase #5	$156.41	10.226%	$172.4045	$172.40	$172.40	$172.40
Purchase #6	$202.66	3.817%	$210.3955	$210.40	$210.40	$210.40
Purchase #7	$54.32	9.591%	$59.5298	$59.53	$59.55	$59.50
7 purchase totals =	$966.95		$1,058.1369	$1,058.13	$1,058.15	$1,058.10