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	$104.58	3.214%	$107.9412	$107.94	$107.95	$107.90
Purchase #2	$32.76	8.223%	$35.4539	$35.45	$35.45	$35.50
Purchase #3	$211.64	10.579%	$234.0294	$234.03	$234.05	$234.00
Purchase #4	$50.69	7.869%	$54.6788	$54.68	$54.70	$54.70
Purchase #5	$100.71	11.356%	$112.1466	$112.15	$112.15	$112.10
Purchase #6	$142.76	6.298%	$151.751	$151.75	$151.75	$151.80
Purchase #7	$73.73	9.236%	$80.5397	$80.54	$80.55	$80.50
7 purchase totals =	$716.87		$776.5406	$776.54	$776.60	$776.50