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	$151.54	9.286%	$165.612	$165.61	$165.60	$165.60
Purchase #2	$120.38	10.593%	$133.1319	$133.13	$133.15	$133.10
Purchase #3	$238.43	6.751%	$254.5264	$254.53	$254.55	$254.50
Purchase #4	$102.60	13.140%	$116.0816	$116.08	$116.10	$116.10
Purchase #5	$120.34	11.284%	$133.9192	$133.92	$133.90	$133.90
Purchase #6	$236.55	11.368%	$263.441	$263.44	$263.45	$263.40
Purchase #7	$86.98	4.268%	$90.6923	$90.69	$90.70	$90.70
7 purchase totals =	$1,056.82		$1,157.4044	$1,157.40	$1,157.45	$1,157.30