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	$231.85	5.295%	$244.1265	$244.13	$244.15	$244.10
Purchase #2	$84.29	7.148%	$90.315	$90.32	$90.30	$90.30
Purchase #3	$83.86	9.173%	$91.5525	$91.55	$91.55	$91.60
Purchase #4	$23.66	6.104%	$25.1042	$25.10	$25.10	$25.10
Purchase #5	$250.76	4.117%	$261.0838	$261.08	$261.10	$261.10
Purchase #6	$234.77	6.273%	$249.4971	$249.50	$249.50	$249.50
Purchase #7	$152.34	10.473%	$168.2946	$168.29	$168.30	$168.30
7 purchase totals =	$1,061.53		$1,129.9737	$1,129.97	$1,130.00	$1,130.00