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	$242.84	5.119%	$255.271	$255.27	$255.25	$255.30
Purchase #2	$167.48	7.672%	$180.3291	$180.33	$180.35	$180.30
Purchase #3	$46.36	10.116%	$51.0498	$51.05	$51.05	$51.00
Purchase #4	$37.66	4.688%	$39.4255	$39.43	$39.45	$39.40
Purchase #5	$238.78	10.225%	$263.1953	$263.20	$263.20	$263.20
Purchase #6	$160.30	5.300%	$168.7959	$168.80	$168.80	$168.80
Purchase #7	$94.81	10.722%	$104.9755	$104.98	$105.00	$105.00
7 purchase totals =	$988.23		$1,063.0421	$1,063.06	$1,063.10	$1,063.00