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	$233.76	4.493%	$244.2628	$244.26	$244.25	$244.30
Purchase #2	$121.50	7.415%	$130.5092	$130.51	$130.50	$130.50
Purchase #3	$72.71	8.134%	$78.6242	$78.62	$78.60	$78.60
Purchase #4	$181.59	5.639%	$191.8299	$191.83	$191.85	$191.80
Purchase #5	$60.37	12.654%	$68.0092	$68.01	$68.00	$68.00
Purchase #6	$203.98	6.320%	$216.8715	$216.87	$216.85	$216.90
Purchase #7	$97.84	5.126%	$102.8553	$102.86	$102.85	$102.90
7 purchase totals =	$971.75		$1,032.9621	$1,032.96	$1,032.90	$1,033.00