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	$72.31	11.444%	$80.5852	$80.59	$80.60	$80.60
Purchase #2	$101.77	4.729%	$106.5827	$106.58	$106.60	$106.60
Purchase #3	$31.85	10.688%	$35.2541	$35.25	$35.25	$35.30
Purchase #4	$197.36	6.180%	$209.5568	$209.56	$209.55	$209.60
Purchase #5	$80.44	12.785%	$90.7243	$90.72	$90.70	$90.70
Purchase #6	$41.77	4.708%	$43.7365	$43.74	$43.75	$43.70
Purchase #7	$112.76	7.233%	$120.9159	$120.92	$120.90	$120.90
7 purchase totals =	$638.26		$687.3555	$687.36	$687.35	$687.40