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	$154.74	8.206%	$167.438	$167.44	$167.45	$167.40
Purchase #2	$60.34	11.724%	$67.4143	$67.41	$67.40	$67.40
Purchase #3	$131.30	10.716%	$145.3701	$145.37	$145.35	$145.40
Purchase #4	$99.88	10.441%	$110.3085	$110.31	$110.30	$110.30
Purchase #5	$162.92	4.275%	$169.8848	$169.88	$169.90	$169.90
Purchase #6	$117.86	11.149%	$131.0002	$131.00	$131.00	$131.00
Purchase #7	$148.36	7.529%	$159.53	$159.53	$159.55	$159.50
7 purchase totals =	$875.40		$950.9459	$950.94	$950.95	$950.90