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	$210.33	5.809%	$222.5481	$222.55	$222.55	$222.50
Purchase #2	$70.54	10.807%	$78.1633	$78.16	$78.15	$78.20
Purchase #3	$237.50	4.747%	$248.7741	$248.77	$248.75	$248.80
Purchase #4	$133.65	7.279%	$143.3784	$143.38	$143.40	$143.40
Purchase #5	$218.88	9.249%	$239.1242	$239.12	$239.10	$239.10
Purchase #6	$12.32	13.311%	$13.9599	$13.96	$13.95	$14.00
Purchase #7	$69.83	3.333%	$72.1574	$72.16	$72.15	$72.20
7 purchase totals =	$953.05		$1,018.1054	$1,018.10	$1,018.05	$1,018.20