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	$25.35	9.476%	$27.7522	$27.75	$27.75	$27.80
Purchase #2	$191.57	6.290%	$203.6198	$203.62	$203.60	$203.60
Purchase #3	$233.31	3.561%	$241.6182	$241.62	$241.60	$241.60
Purchase #4	$163.56	7.226%	$175.3788	$175.38	$175.40	$175.40
Purchase #5	$40.91	3.155%	$42.2007	$42.20	$42.20	$42.20
Purchase #6	$113.47	12.601%	$127.7684	$127.77	$127.75	$127.80
Purchase #7	$182.74	7.501%	$196.4473	$196.45	$196.45	$196.40
7 purchase totals =	$950.91		$1,014.7854	$1,014.79	$1,014.75	$1,014.80