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	$223.64	10.193%	$246.4356	$246.44	$246.45	$246.40
Purchase #2	$152.59	10.144%	$168.0687	$168.07	$168.05	$168.10
Purchase #3	$79.41	3.572%	$82.2465	$82.25	$82.25	$82.20
Purchase #4	$70.55	11.341%	$78.5511	$78.55	$78.55	$78.60
Purchase #5	$156.37	10.388%	$172.6137	$172.61	$172.60	$172.60
Purchase #6	$64.85	6.259%	$68.909	$68.91	$68.90	$68.90
Purchase #7	$19.77	3.611%	$20.4839	$20.48	$20.50	$20.50
7 purchase totals =	$767.18		$837.3085	$837.31	$837.30	$837.30