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	$93.31	5.292%	$98.248	$98.25	$98.25	$98.20
Purchase #2	$144.63	13.394%	$164.0017	$164.00	$164.00	$164.00
Purchase #3	$104.33	5.616%	$110.1892	$110.19	$110.20	$110.20
Purchase #4	$119.75	6.473%	$127.5014	$127.50	$127.50	$127.50
Purchase #5	$116.27	12.839%	$131.1979	$131.20	$131.20	$131.20
Purchase #6	$196.65	13.606%	$223.4062	$223.41	$223.40	$223.40
Purchase #7	$150.71	7.599%	$162.1625	$162.16	$162.15	$162.20
7 purchase totals =	$925.65		$1,016.7069	$1,016.71	$1,016.70	$1,016.70