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	$203.82	9.517%	$223.2175	$223.22	$223.20	$223.20
Purchase #2	$116.92	9.379%	$127.8859	$127.89	$127.90	$127.90
Purchase #3	$14.82	5.426%	$15.6241	$15.62	$15.60	$15.60
Purchase #4	$108.66	6.719%	$115.9609	$115.96	$115.95	$116.00
Purchase #5	$191.41	3.469%	$198.05	$198.05	$198.05	$198.10
Purchase #6	$118.80	3.681%	$123.173	$123.17	$123.15	$123.20
Purchase #7	$188.52	13.234%	$213.4687	$213.47	$213.45	$213.50
7 purchase totals =	$942.95		$1,017.3801	$1,017.38	$1,017.30	$1,017.50