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	$98.43	10.635%	$108.898	$108.90	$108.90	$108.90
Purchase #2	$152.96	7.453%	$164.3601	$164.36	$164.35	$164.40
Purchase #3	$239.81	12.818%	$270.5488	$270.55	$270.55	$270.50
Purchase #4	$160.44	10.430%	$177.1739	$177.17	$177.15	$177.20
Purchase #5	$171.79	8.547%	$186.4729	$186.47	$186.45	$186.50
Purchase #6	$55.54	7.753%	$59.846	$59.85	$59.85	$59.80
Purchase #7	$47.35	9.734%	$51.959	$51.96	$51.95	$52.00
7 purchase totals =	$926.32		$1,019.2587	$1,019.26	$1,019.20	$1,019.30