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	$86.53	11.797%	$96.7379	$96.74	$96.75	$96.70
Purchase #2	$198.91	5.323%	$209.498	$209.50	$209.50	$209.50
Purchase #3	$54.93	8.132%	$59.3969	$59.40	$59.40	$59.40
Purchase #4	$51.94	8.669%	$56.4427	$56.44	$56.45	$56.40
Purchase #5	$96.67	9.781%	$106.1253	$106.13	$106.15	$106.10
Purchase #6	$184.30	13.793%	$209.7205	$209.72	$209.70	$209.70
Purchase #7	$124.31	10.680%	$137.5863	$137.59	$137.60	$137.60
7 purchase totals =	$797.59		$875.5076	$875.52	$875.55	$875.40