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	$137.68	5.233%	$144.8848	$144.88	$144.90	$144.90
Purchase #2	$80.90	7.229%	$86.7483	$86.75	$86.75	$86.70
Purchase #3	$150.91	9.774%	$165.6599	$165.66	$165.65	$165.70
Purchase #4	$185.72	10.537%	$205.2893	$205.29	$205.30	$205.30
Purchase #5	$239.50	4.312%	$249.8272	$249.83	$249.85	$249.80
Purchase #6	$92.73	7.394%	$99.5865	$99.59	$99.60	$99.60
Purchase #7	$160.39	5.231%	$168.78	$168.78	$168.80	$168.80
7 purchase totals =	$1,047.83		$1,120.7760	$1,120.78	$1,120.85	$1,120.80