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	$123.76	7.564%	$133.1212	$133.12	$133.10	$133.10
Purchase #2	$75.86	6.168%	$80.539	$80.54	$80.55	$80.50
Purchase #3	$20.80	5.195%	$21.8806	$21.88	$21.90	$21.90
Purchase #4	$87.31	4.873%	$91.5646	$91.56	$91.55	$91.60
Purchase #5	$120.83	10.725%	$133.789	$133.79	$133.80	$133.80
Purchase #6	$133.78	12.818%	$150.9279	$150.93	$150.95	$150.90
Purchase #7	$174.40	3.570%	$180.6261	$180.63	$180.65	$180.60
7 purchase totals =	$736.74		$792.4484	$792.45	$792.50	$792.40