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	$151.58	13.223%	$171.6234	$171.62	$171.60	$171.60
Purchase #2	$64.45	13.507%	$73.1553	$73.16	$73.15	$73.20
Purchase #3	$16.84	3.280%	$17.3924	$17.39	$17.40	$17.40
Purchase #4	$119.59	3.150%	$123.3571	$123.36	$123.35	$123.40
Purchase #5	$196.83	7.298%	$211.1947	$211.19	$211.20	$211.20
Purchase #6	$175.61	3.357%	$181.5052	$181.51	$181.50	$181.50
Purchase #7	$79.68	12.713%	$89.8097	$89.81	$89.80	$89.80
7 purchase totals =	$804.58		$868.0378	$868.04	$868.00	$868.10