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	$170.38	6.468%	$181.4002	$181.40	$181.40	$181.40
Purchase #2	$180.39	7.461%	$193.8489	$193.85	$193.85	$193.80
Purchase #3	$139.33	3.606%	$144.3542	$144.35	$144.35	$144.40
Purchase #4	$213.98	10.148%	$235.6947	$235.69	$235.70	$235.70
Purchase #5	$111.86	10.618%	$123.7373	$123.74	$123.75	$123.70
Purchase #6	$192.60	3.592%	$199.5182	$199.52	$199.50	$199.50
Purchase #7	$19.80	5.591%	$20.907	$20.91	$20.90	$20.90
7 purchase totals =	$1,028.34		$1,099.4605	$1,099.46	$1,099.45	$1,099.40