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	$160.38	3.847%	$166.5498	$166.55	$166.55	$166.50
Purchase #2	$26.74	4.415%	$27.9206	$27.92	$27.90	$27.90
Purchase #3	$68.99	4.814%	$72.3112	$72.31	$72.30	$72.30
Purchase #4	$162.91	4.230%	$169.8011	$169.80	$169.80	$169.80
Purchase #5	$124.77	5.327%	$131.4165	$131.42	$131.40	$131.40
Purchase #6	$105.59	10.243%	$116.4056	$116.41	$116.40	$116.40
Purchase #7	$181.52	3.390%	$187.6735	$187.67	$187.65	$187.70
7 purchase totals =	$830.90		$872.0783	$872.08	$872.00	$872.00