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	$156.69	7.244%	$168.0406	$168.04	$168.05	$168.00
Purchase #2	$243.82	13.586%	$276.9454	$276.95	$276.95	$276.90
Purchase #3	$20.45	3.413%	$21.148	$21.15	$21.15	$21.10
Purchase #4	$132.43	11.440%	$147.58	$147.58	$147.60	$147.60
Purchase #5	$98.27	6.757%	$104.9101	$104.91	$104.90	$104.90
Purchase #6	$243.55	5.315%	$256.4947	$256.49	$256.50	$256.50
Purchase #7	$129.98	3.811%	$134.9335	$134.93	$134.95	$134.90
7 purchase totals =	$1,025.19		$1,110.0523	$1,110.05	$1,110.10	$1,109.90