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	$110.71	11.455%	$123.3918	$123.39	$123.40	$123.40
Purchase #2	$209.63	9.258%	$229.0375	$229.04	$229.05	$229.00
Purchase #3	$189.41	5.790%	$200.3768	$200.38	$200.40	$200.40
Purchase #4	$9.51	10.853%	$10.5421	$10.54	$10.55	$10.50
Purchase #5	$109.36	4.159%	$113.9083	$113.91	$113.90	$113.90
Purchase #6	$210.81	4.804%	$220.9373	$220.94	$220.95	$220.90
Purchase #7	$222.48	4.691%	$232.9165	$232.92	$232.90	$232.90
7 purchase totals =	$1,061.91		$1,131.1103	$1,131.12	$1,131.15	$1,131.00