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	$170.55	7.607%	$183.5237	$183.52	$183.50	$183.50
Purchase #2	$57.68	8.191%	$62.4046	$62.40	$62.40	$62.40
Purchase #3	$167.50	4.165%	$174.4764	$174.48	$174.50	$174.50
Purchase #4	$188.55	13.267%	$213.5649	$213.56	$213.55	$213.60
Purchase #5	$33.46	10.855%	$37.0921	$37.09	$37.10	$37.10
Purchase #6	$62.52	6.780%	$66.7589	$66.76	$66.75	$66.80
Purchase #7	$168.97	3.105%	$174.2165	$174.22	$174.20	$174.20
7 purchase totals =	$849.23		$912.0371	$912.03	$912.00	$912.10