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	$68.91	10.396%	$76.0739	$76.07	$76.05	$76.10
Purchase #2	$234.26	3.337%	$242.0773	$242.08	$242.10	$242.10
Purchase #3	$80.65	11.767%	$90.1401	$90.14	$90.15	$90.10
Purchase #4	$221.86	10.501%	$245.1575	$245.16	$245.15	$245.20
Purchase #5	$221.25	7.758%	$238.4146	$238.41	$238.40	$238.40
Purchase #6	$76.29	11.254%	$84.8757	$84.88	$84.90	$84.90
Purchase #7	$24.65	11.492%	$27.4828	$27.48	$27.50	$27.50
7 purchase totals =	$927.87		$1,004.2219	$1,004.22	$1,004.25	$1,004.30