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	$145.64	13.292%	$164.9985	$165.00	$165.00	$165.00
Purchase #2	$148.96	10.131%	$164.0511	$164.05	$164.05	$164.10
Purchase #3	$222.69	4.168%	$231.9717	$231.97	$231.95	$232.00
Purchase #4	$165.78	5.500%	$174.8979	$174.90	$174.90	$174.90
Purchase #5	$134.29	8.288%	$145.42	$145.42	$145.40	$145.40
Purchase #6	$96.41	3.414%	$99.7014	$99.70	$99.70	$99.70
Purchase #7	$172.54	7.545%	$185.5581	$185.56	$185.55	$185.60
7 purchase totals =	$1,086.31		$1,166.5987	$1,166.60	$1,166.55	$1,166.70