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	$163.85	6.771%	$174.9443	$174.94	$174.95	$174.90
Purchase #2	$239.32	6.348%	$254.512	$254.51	$254.50	$254.50
Purchase #3	$91.37	5.166%	$96.0902	$96.09	$96.10	$96.10
Purchase #4	$219.76	8.449%	$238.3275	$238.33	$238.35	$238.30
Purchase #5	$80.39	4.286%	$83.8355	$83.84	$83.85	$83.80
Purchase #6	$93.62	3.194%	$96.6102	$96.61	$96.60	$96.60
Purchase #7	$187.27	5.801%	$198.1335	$198.13	$198.15	$198.10
7 purchase totals =	$1,075.58		$1,142.4532	$1,142.45	$1,142.50	$1,142.30