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	$139.87	7.603%	$150.5043	$150.50	$150.50	$150.50
Purchase #2	$182.34	9.303%	$199.3031	$199.30	$199.30	$199.30
Purchase #3	$51.41	4.699%	$53.8258	$53.83	$53.85	$53.80
Purchase #4	$101.97	7.118%	$109.2282	$109.23	$109.25	$109.20
Purchase #5	$178.89	3.571%	$185.2782	$185.28	$185.30	$185.30
Purchase #6	$225.69	7.432%	$242.4633	$242.46	$242.45	$242.50
Purchase #7	$82.25	4.603%	$86.036	$86.04	$86.05	$86.00
7 purchase totals =	$962.42		$1,026.6389	$1,026.64	$1,026.70	$1,026.60