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	$236.37	11.873%	$264.4342	$264.43	$264.45	$264.40
Purchase #2	$134.97	11.149%	$150.0178	$150.02	$150.00	$150.00
Purchase #3	$61.52	10.414%	$67.9267	$67.93	$67.95	$67.90
Purchase #4	$40.28	13.472%	$45.7065	$45.71	$45.70	$45.70
Purchase #5	$238.72	10.229%	$263.1387	$263.14	$263.15	$263.10
Purchase #6	$105.67	8.564%	$114.7196	$114.72	$114.70	$114.70
Purchase #7	$217.96	3.853%	$226.358	$226.36	$226.35	$226.40
7 purchase totals =	$1,035.49		$1,132.3015	$1,132.31	$1,132.30	$1,132.20