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	$233.30	12.432%	$262.3039	$262.30	$262.30	$262.30
Purchase #2	$18.64	6.627%	$19.8753	$19.88	$19.90	$19.90
Purchase #3	$131.38	8.302%	$142.2872	$142.29	$142.30	$142.30
Purchase #4	$16.46	5.860%	$17.4246	$17.42	$17.40	$17.40
Purchase #5	$53.64	12.277%	$60.2254	$60.23	$60.25	$60.20
Purchase #6	$86.46	3.620%	$89.5899	$89.59	$89.60	$89.60
Purchase #7	$114.72	11.691%	$128.1319	$128.13	$128.15	$128.10
7 purchase totals =	$654.60		$719.8382	$719.84	$719.90	$719.80