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	$213.64	12.720%	$240.815	$240.82	$240.80	$240.80
Purchase #2	$180.84	13.422%	$205.1123	$205.11	$205.10	$205.10
Purchase #3	$56.82	3.810%	$58.9848	$58.98	$59.00	$59.00
Purchase #4	$114.96	12.691%	$129.5496	$129.55	$129.55	$129.50
Purchase #5	$216.88	13.220%	$245.5515	$245.55	$245.55	$245.60
Purchase #6	$85.84	5.151%	$90.2616	$90.26	$90.25	$90.30
Purchase #7	$180.97	9.718%	$198.5567	$198.56	$198.55	$198.60
7 purchase totals =	$1,049.95		$1,168.8315	$1,168.83	$1,168.80	$1,168.90