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	$56.69	10.111%	$62.4219	$62.42	$62.40	$62.40
Purchase #2	$116.86	11.807%	$130.6577	$130.66	$130.65	$130.70
Purchase #3	$142.86	9.276%	$156.1117	$156.11	$156.10	$156.10
Purchase #4	$16.67	5.592%	$17.6022	$17.60	$17.60	$17.60
Purchase #5	$103.92	5.360%	$109.4901	$109.49	$109.50	$109.50
Purchase #6	$79.41	3.592%	$82.2624	$82.26	$82.25	$82.30
Purchase #7	$177.85	5.630%	$187.863	$187.86	$187.85	$187.90
7 purchase totals =	$694.26		$746.4090	$746.40	$746.35	$746.50