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	$174.47	5.822%	$184.6276	$184.63	$184.65	$184.60
Purchase #2	$103.63	5.570%	$109.4022	$109.40	$109.40	$109.40
Purchase #3	$207.72	10.682%	$229.9087	$229.91	$229.90	$229.90
Purchase #4	$43.61	12.185%	$48.9239	$48.92	$48.90	$48.90
Purchase #5	$158.73	5.553%	$167.5443	$167.54	$167.55	$167.50
Purchase #6	$95.56	7.805%	$103.0185	$103.02	$103.00	$103.00
Purchase #7	$164.90	10.384%	$182.0232	$182.02	$182.00	$182.00
7 purchase totals =	$948.62		$1,025.4484	$1,025.44	$1,025.40	$1,025.30