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	$201.52	9.811%	$221.2911	$221.29	$221.30	$221.30
Purchase #2	$36.51	3.788%	$37.893	$37.89	$37.90	$37.90
Purchase #3	$97.47	13.320%	$110.453	$110.45	$110.45	$110.50
Purchase #4	$196.28	12.373%	$220.5657	$220.57	$220.55	$220.60
Purchase #5	$171.53	12.594%	$193.1325	$193.13	$193.15	$193.10
Purchase #6	$127.98	8.862%	$139.3216	$139.32	$139.30	$139.30
Purchase #7	$221.93	8.148%	$240.0129	$240.01	$240.00	$240.00
7 purchase totals =	$1,053.22		$1,162.6698	$1,162.66	$1,162.65	$1,162.70