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	$74.82	8.699%	$81.3286	$81.33	$81.35	$81.30
Purchase #2	$222.38	10.434%	$245.5831	$245.58	$245.60	$245.60
Purchase #3	$79.99	13.441%	$90.7415	$90.74	$90.75	$90.70
Purchase #4	$152.79	13.786%	$173.8536	$173.85	$173.85	$173.90
Purchase #5	$156.42	7.146%	$167.5978	$167.60	$167.60	$167.60
Purchase #6	$199.50	6.739%	$212.9443	$212.94	$212.95	$212.90
Purchase #7	$59.26	13.247%	$67.1102	$67.11	$67.10	$67.10
7 purchase totals =	$945.16		$1,039.1591	$1,039.15	$1,039.20	$1,039.10