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	$150.48	13.656%	$171.0295	$171.03	$171.05	$171.00
Purchase #2	$14.57	12.507%	$16.3923	$16.39	$16.40	$16.40
Purchase #3	$155.37	4.856%	$162.9148	$162.91	$162.90	$162.90
Purchase #4	$111.97	13.682%	$127.2897	$127.29	$127.30	$127.30
Purchase #5	$207.78	9.268%	$227.0371	$227.04	$227.05	$227.00
Purchase #6	$106.93	7.444%	$114.8899	$114.89	$114.90	$114.90
Purchase #7	$218.98	11.265%	$243.6481	$243.65	$243.65	$243.60
7 purchase totals =	$966.08		$1,063.2014	$1,063.20	$1,063.25	$1,063.10