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	$164.76	6.109%	$174.8252	$174.83	$174.85	$174.80
Purchase #2	$106.99	11.643%	$119.4468	$119.45	$119.45	$119.40
Purchase #3	$141.90	10.296%	$156.51	$156.51	$156.50	$156.50
Purchase #4	$156.38	9.445%	$171.1501	$171.15	$171.15	$171.20
Purchase #5	$124.47	6.769%	$132.8954	$132.90	$132.90	$132.90
Purchase #6	$167.67	12.247%	$188.2045	$188.20	$188.20	$188.20
Purchase #7	$159.97	7.557%	$172.0589	$172.06	$172.05	$172.10
7 purchase totals =	$1,022.14		$1,115.0909	$1,115.10	$1,115.10	$1,115.10