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	$120.35	11.407%	$134.0783	$134.08	$134.10	$134.10
Purchase #2	$83.95	8.762%	$91.3057	$91.31	$91.30	$91.30
Purchase #3	$137.49	5.370%	$144.8732	$144.87	$144.85	$144.90
Purchase #4	$89.96	7.403%	$96.6197	$96.62	$96.60	$96.60
Purchase #5	$152.25	5.484%	$160.5994	$160.60	$160.60	$160.60
Purchase #6	$223.94	13.394%	$253.9345	$253.93	$253.95	$253.90
Purchase #7	$151.72	8.627%	$164.8089	$164.81	$164.80	$164.80
7 purchase totals =	$959.66		$1,046.2197	$1,046.22	$1,046.20	$1,046.20