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	$164.85	12.275%	$185.0853	$185.09	$185.10	$185.10
Purchase #2	$71.28	12.843%	$80.4345	$80.43	$80.45	$80.40
Purchase #3	$37.99	12.140%	$42.602	$42.60	$42.60	$42.60
Purchase #4	$143.59	7.817%	$154.8144	$154.81	$154.80	$154.80
Purchase #5	$27.91	5.272%	$29.3814	$29.38	$29.40	$29.40
Purchase #6	$86.61	11.681%	$96.7269	$96.73	$96.75	$96.70
Purchase #7	$102.68	13.267%	$116.3026	$116.30	$116.30	$116.30
7 purchase totals =	$634.91		$705.3471	$705.34	$705.40	$705.30