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	$214.75	4.234%	$223.8425	$223.84	$223.85	$223.80
Purchase #2	$166.68	13.401%	$189.0168	$189.02	$189.00	$189.00
Purchase #3	$43.40	11.232%	$48.2747	$48.27	$48.25	$48.30
Purchase #4	$185.98	5.600%	$196.3949	$196.39	$196.40	$196.40
Purchase #5	$202.90	3.223%	$209.4395	$209.44	$209.45	$209.40
Purchase #6	$146.90	4.191%	$153.0566	$153.06	$153.05	$153.10
Purchase #7	$20.71	5.653%	$21.8807	$21.88	$21.90	$21.90
7 purchase totals =	$981.32		$1,041.9057	$1,041.90	$1,041.90	$1,041.90