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	$225.52	5.757%	$238.5032	$238.50	$238.50	$238.50
Purchase #2	$70.76	3.673%	$73.359	$73.36	$73.35	$73.40
Purchase #3	$132.61	4.582%	$138.6862	$138.69	$138.70	$138.70
Purchase #4	$61.43	9.607%	$67.3316	$67.33	$67.35	$67.30
Purchase #5	$232.32	12.846%	$262.1638	$262.16	$262.15	$262.20
Purchase #6	$57.35	4.265%	$59.796	$59.80	$59.80	$59.80
Purchase #7	$48.46	5.165%	$50.963	$50.96	$50.95	$51.00
7 purchase totals =	$828.45		$890.8028	$890.80	$890.80	$890.90