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	$230.25	5.530%	$242.9828	$242.98	$243.00	$243.00
Purchase #2	$245.37	12.673%	$276.4657	$276.47	$276.45	$276.50
Purchase #3	$28.57	3.770%	$29.6471	$29.65	$29.65	$29.60
Purchase #4	$42.43	4.514%	$44.3453	$44.35	$44.35	$44.30
Purchase #5	$86.92	3.190%	$89.6927	$89.69	$89.70	$89.70
Purchase #6	$205.59	8.527%	$223.1207	$223.12	$223.10	$223.10
Purchase #7	$230.47	3.303%	$238.0824	$238.08	$238.10	$238.10
7 purchase totals =	$1,069.60		$1,144.3367	$1,144.34	$1,144.35	$1,144.30