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	$179.67	13.595%	$204.0961	$204.10	$204.10	$204.10
Purchase #2	$45.68	7.539%	$49.1238	$49.12	$49.10	$49.10
Purchase #3	$82.76	3.440%	$85.6069	$85.61	$85.60	$85.60
Purchase #4	$65.90	10.144%	$72.5849	$72.58	$72.60	$72.60
Purchase #5	$179.25	9.260%	$195.8486	$195.85	$195.85	$195.80
Purchase #6	$224.69	8.865%	$244.6088	$244.61	$244.60	$244.60
Purchase #7	$191.33	7.670%	$206.005	$206.01	$206.00	$206.00
7 purchase totals =	$969.28		$1,057.8741	$1,057.88	$1,057.85	$1,057.80