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	$220.76	5.810%	$233.5862	$233.59	$233.60	$233.60
Purchase #2	$233.78	11.802%	$261.3707	$261.37	$261.35	$261.40
Purchase #3	$200.59	10.701%	$222.0551	$222.06	$222.05	$222.10
Purchase #4	$64.70	4.241%	$67.4439	$67.44	$67.45	$67.40
Purchase #5	$5.75	4.271%	$5.9956	$6.00	$6.00	$6.00
Purchase #6	$49.35	8.444%	$53.5171	$53.52	$53.50	$53.50
Purchase #7	$162.27	4.380%	$169.3774	$169.38	$169.40	$169.40
7 purchase totals =	$937.20		$1,013.3460	$1,013.36	$1,013.35	$1,013.40