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	$117.84	8.547%	$127.9118	$127.91	$127.90	$127.90
Purchase #2	$101.62	7.817%	$109.5636	$109.56	$109.55	$109.60
Purchase #3	$53.86	5.572%	$56.8611	$56.86	$56.85	$56.90
Purchase #4	$149.39	4.512%	$156.1305	$156.13	$156.15	$156.10
Purchase #5	$144.94	7.342%	$155.5815	$155.58	$155.60	$155.60
Purchase #6	$46.44	11.813%	$51.926	$51.93	$51.95	$51.90
Purchase #7	$112.58	11.564%	$125.5988	$125.60	$125.60	$125.60
7 purchase totals =	$726.67		$783.5733	$783.57	$783.60	$783.60