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	$143.46	11.612%	$160.1186	$160.12	$160.10	$160.10
Purchase #2	$101.61	4.674%	$106.3593	$106.36	$106.35	$106.40
Purchase #3	$220.37	6.328%	$234.315	$234.32	$234.30	$234.30
Purchase #4	$61.47	4.644%	$64.3247	$64.32	$64.30	$64.30
Purchase #5	$40.59	4.529%	$42.4283	$42.43	$42.45	$42.40
Purchase #6	$51.67	4.317%	$53.9006	$53.90	$53.90	$53.90
Purchase #7	$115.83	6.268%	$123.0902	$123.09	$123.10	$123.10
7 purchase totals =	$735.00		$784.5367	$784.54	$784.50	$784.50