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	$142.59	5.810%	$150.8745	$150.87	$150.85	$150.90
Purchase #2	$8.61	11.463%	$9.597	$9.60	$9.60	$9.60
Purchase #3	$52.27	13.515%	$59.3343	$59.33	$59.35	$59.30
Purchase #4	$177.88	12.585%	$200.2662	$200.27	$200.25	$200.30
Purchase #5	$63.88	3.133%	$65.8814	$65.88	$65.90	$65.90
Purchase #6	$140.73	13.254%	$159.3824	$159.38	$159.40	$159.40
Purchase #7	$154.68	13.118%	$174.9709	$174.97	$174.95	$175.00
7 purchase totals =	$740.64		$820.3067	$820.30	$820.30	$820.40