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	$210.67	8.169%	$227.8796	$227.88	$227.90	$227.90
Purchase #2	$112.50	6.279%	$119.5639	$119.56	$119.55	$119.60
Purchase #3	$209.32	13.767%	$238.1371	$238.14	$238.15	$238.10
Purchase #4	$39.46	10.669%	$43.67	$43.67	$43.65	$43.70
Purchase #5	$59.37	3.475%	$61.4331	$61.43	$61.45	$61.40
Purchase #6	$63.98	5.354%	$67.4055	$67.41	$67.40	$67.40
Purchase #7	$62.80	13.793%	$71.462	$71.46	$71.45	$71.50
7 purchase totals =	$758.10		$829.5512	$829.55	$829.55	$829.60