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	$166.28	8.449%	$180.329	$180.33	$180.35	$180.30
Purchase #2	$49.25	5.738%	$52.076	$52.08	$52.10	$52.10
Purchase #3	$162.92	13.613%	$185.0983	$185.10	$185.10	$185.10
Purchase #4	$194.58	13.379%	$220.6129	$220.61	$220.60	$220.60
Purchase #5	$215.33	12.315%	$241.8479	$241.85	$241.85	$241.80
Purchase #6	$92.59	5.785%	$97.9463	$97.95	$97.95	$97.90
Purchase #7	$90.53	9.861%	$99.4572	$99.46	$99.45	$99.50
7 purchase totals =	$971.48		$1,077.3676	$1,077.38	$1,077.40	$1,077.30