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	$198.57	11.808%	$222.0171	$222.02	$222.00	$222.00
Purchase #2	$126.36	5.626%	$133.469	$133.47	$133.45	$133.50
Purchase #3	$118.25	4.124%	$123.1266	$123.13	$123.15	$123.10
Purchase #4	$45.52	6.359%	$48.4146	$48.41	$48.40	$48.40
Purchase #5	$94.37	9.254%	$103.103	$103.10	$103.10	$103.10
Purchase #6	$218.76	4.736%	$229.1205	$229.12	$229.10	$229.10
Purchase #7	$111.82	12.716%	$126.039	$126.04	$126.05	$126.00
7 purchase totals =	$913.65		$985.2898	$985.29	$985.25	$985.20