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	$122.35	3.470%	$126.5955	$126.60	$126.60	$126.60
Purchase #2	$229.86	5.779%	$243.1436	$243.14	$243.15	$243.10
Purchase #3	$223.81	6.373%	$238.0734	$238.07	$238.05	$238.10
Purchase #4	$135.71	4.737%	$142.1386	$142.14	$142.15	$142.10
Purchase #5	$150.76	7.544%	$162.1333	$162.13	$162.15	$162.10
Purchase #6	$112.81	13.419%	$127.948	$127.95	$127.95	$127.90
Purchase #7	$134.94	12.748%	$152.1422	$152.14	$152.15	$152.10
7 purchase totals =	$1,110.24		$1,192.1746	$1,192.17	$1,192.20	$1,192.00