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	$148.80	10.530%	$164.4686	$164.47	$164.45	$164.50
Purchase #2	$122.54	7.417%	$131.6288	$131.63	$131.65	$131.60
Purchase #3	$19.90	10.511%	$21.9917	$21.99	$22.00	$22.00
Purchase #4	$85.81	10.806%	$95.0826	$95.08	$95.10	$95.10
Purchase #5	$42.52	10.654%	$47.0501	$47.05	$47.05	$47.10
Purchase #6	$94.56	4.547%	$98.8596	$98.86	$98.85	$98.90
Purchase #7	$152.90	12.318%	$171.7342	$171.73	$171.75	$171.70
7 purchase totals =	$667.03		$730.8156	$730.81	$730.85	$730.90