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	$245.78	11.116%	$273.1009	$273.10	$273.10	$273.10
Purchase #2	$37.94	10.815%	$42.0432	$42.04	$42.05	$42.00
Purchase #3	$223.46	4.382%	$233.252	$233.25	$233.25	$233.30
Purchase #4	$100.31	11.655%	$112.0011	$112.00	$112.00	$112.00
Purchase #5	$71.46	6.587%	$76.1671	$76.17	$76.15	$76.20
Purchase #6	$161.29	3.557%	$167.0271	$167.03	$167.05	$167.00
Purchase #7	$106.95	10.625%	$118.3134	$118.31	$118.30	$118.30
7 purchase totals =	$947.19		$1,021.9048	$1,021.90	$1,021.90	$1,021.90