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	$149.92	6.718%	$159.9916	$159.99	$160.00	$160.00
Purchase #2	$86.81	3.171%	$89.5627	$89.56	$89.55	$89.60
Purchase #3	$237.51	3.227%	$245.1744	$245.17	$245.15	$245.20
Purchase #4	$218.90	6.188%	$232.4455	$232.45	$232.45	$232.40
Purchase #5	$159.41	5.208%	$167.7121	$167.71	$167.70	$167.70
Purchase #6	$69.51	4.429%	$72.5886	$72.59	$72.60	$72.60
Purchase #7	$222.45	8.465%	$241.2804	$241.28	$241.30	$241.30
7 purchase totals =	$1,144.51		$1,208.7553	$1,208.75	$1,208.75	$1,208.80