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	$235.55	10.820%	$261.0365	$261.04	$261.05	$261.00
Purchase #2	$197.27	8.131%	$213.31	$213.31	$213.30	$213.30
Purchase #3	$184.46	3.337%	$190.6154	$190.62	$190.60	$190.60
Purchase #4	$152.72	10.166%	$168.2455	$168.25	$168.25	$168.20
Purchase #5	$216.84	5.614%	$229.0134	$229.01	$229.00	$229.00
Purchase #6	$152.37	8.670%	$165.5805	$165.58	$165.60	$165.60
Purchase #7	$97.89	7.683%	$105.4109	$105.41	$105.40	$105.40
7 purchase totals =	$1,237.10		$1,333.2122	$1,333.22	$1,333.20	$1,333.10