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	$204.63	6.417%	$217.7611	$217.76	$217.75	$217.80
Purchase #2	$167.82	3.649%	$173.9438	$173.94	$173.95	$173.90
Purchase #3	$219.86	4.134%	$228.949	$228.95	$228.95	$228.90
Purchase #4	$140.33	12.810%	$158.3063	$158.31	$158.30	$158.30
Purchase #5	$224.36	13.239%	$254.063	$254.06	$254.05	$254.10
Purchase #6	$172.44	8.423%	$186.9646	$186.96	$186.95	$187.00
Purchase #7	$56.75	5.537%	$59.8922	$59.89	$59.90	$59.90
7 purchase totals =	$1,186.19		$1,279.8800	$1,279.87	$1,279.85	$1,279.90