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	$241.37	3.134%	$248.9345	$248.93	$248.95	$248.90
Purchase #2	$202.88	4.142%	$211.2833	$211.28	$211.30	$211.30
Purchase #3	$80.50	10.530%	$88.9767	$88.98	$89.00	$89.00
Purchase #4	$173.47	13.159%	$196.2969	$196.30	$196.30	$196.30
Purchase #5	$52.84	3.337%	$54.6033	$54.60	$54.60	$54.60
Purchase #6	$209.85	3.218%	$216.603	$216.60	$216.60	$216.60
Purchase #7	$174.68	3.522%	$180.8322	$180.83	$180.85	$180.80
7 purchase totals =	$1,135.59		$1,197.5299	$1,197.52	$1,197.60	$1,197.50