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	$126.55	6.560%	$134.8517	$134.85	$134.85	$134.90
Purchase #2	$114.30	9.739%	$125.4317	$125.43	$125.45	$125.40
Purchase #3	$119.91	5.181%	$126.1225	$126.12	$126.10	$126.10
Purchase #4	$51.88	10.634%	$57.3969	$57.40	$57.40	$57.40
Purchase #5	$70.51	10.847%	$78.1582	$78.16	$78.15	$78.20
Purchase #6	$71.38	9.719%	$78.3174	$78.32	$78.30	$78.30
Purchase #7	$206.96	9.408%	$226.4308	$226.43	$226.45	$226.40
7 purchase totals =	$761.49		$826.7092	$826.71	$826.70	$826.70