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	$49.38	10.264%	$54.4484	$54.45	$54.45	$54.40
Purchase #2	$7.37	6.814%	$7.8722	$7.87	$7.85	$7.90
Purchase #3	$42.59	7.244%	$45.6752	$45.68	$45.70	$45.70
Purchase #4	$72.83	9.236%	$79.5566	$79.56	$79.55	$79.60
Purchase #5	$108.83	9.269%	$118.9175	$118.92	$118.90	$118.90
Purchase #6	$204.31	3.826%	$212.1269	$212.13	$212.15	$212.10
Purchase #7	$105.80	3.310%	$109.302	$109.30	$109.30	$109.30
7 purchase totals =	$591.11		$627.8988	$627.91	$627.90	$627.90