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	$175.78	12.680%	$198.0689	$198.07	$198.05	$198.10
Purchase #2	$214.86	13.284%	$243.402	$243.40	$243.40	$243.40
Purchase #3	$75.87	9.231%	$82.8736	$82.87	$82.85	$82.90
Purchase #4	$7.57	13.106%	$8.5621	$8.56	$8.55	$8.60
Purchase #5	$107.95	11.665%	$120.5424	$120.54	$120.55	$120.50
Purchase #6	$250.82	9.468%	$274.5676	$274.57	$274.55	$274.60
Purchase #7	$89.48	11.626%	$99.8829	$99.88	$99.90	$99.90
7 purchase totals =	$922.33		$1,027.8995	$1,027.89	$1,027.85	$1,028.00