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	$156.92	4.546%	$164.0536	$164.05	$164.05	$164.10
Purchase #2	$209.50	6.865%	$223.8822	$223.88	$223.90	$223.90
Purchase #3	$181.36	5.107%	$190.6221	$190.62	$190.60	$190.60
Purchase #4	$77.55	5.154%	$81.5469	$81.55	$81.55	$81.50
Purchase #5	$217.42	10.807%	$240.9166	$240.92	$240.90	$240.90
Purchase #6	$68.31	6.274%	$72.5958	$72.60	$72.60	$72.60
Purchase #7	$143.85	3.550%	$148.9567	$148.96	$148.95	$149.00
7 purchase totals =	$1,054.91		$1,122.5739	$1,122.58	$1,122.55	$1,122.60