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	$49.43	5.330%	$52.0646	$52.06	$52.05	$52.10
Purchase #2	$40.46	7.750%	$43.5957	$43.60	$43.60	$43.60
Purchase #3	$45.25	13.431%	$51.3275	$51.33	$51.35	$51.30
Purchase #4	$85.30	5.499%	$89.9906	$89.99	$90.00	$90.00
Purchase #5	$75.88	12.338%	$85.2421	$85.24	$85.25	$85.20
Purchase #6	$128.25	4.361%	$133.843	$133.84	$133.85	$133.80
Purchase #7	$142.26	7.175%	$152.4672	$152.47	$152.45	$152.50
7 purchase totals =	$566.83		$608.5307	$608.53	$608.55	$608.50