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	$127.83	5.459%	$134.8082	$134.81	$134.80	$134.80
Purchase #2	$218.57	9.173%	$238.6194	$238.62	$238.60	$238.60
Purchase #3	$200.92	10.629%	$222.2758	$222.28	$222.30	$222.30
Purchase #4	$151.61	7.616%	$163.1566	$163.16	$163.15	$163.20
Purchase #5	$233.94	6.267%	$248.601	$248.60	$248.60	$248.60
Purchase #6	$247.68	7.119%	$265.3123	$265.31	$265.30	$265.30
Purchase #7	$127.75	7.596%	$137.4539	$137.45	$137.45	$137.50
7 purchase totals =	$1,308.30		$1,410.2272	$1,410.23	$1,410.20	$1,410.30