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	$98.43	10.842%	$109.1018	$109.10	$109.10	$109.10
Purchase #2	$110.25	5.428%	$116.2344	$116.23	$116.25	$116.20
Purchase #3	$69.72	11.634%	$77.8312	$77.83	$77.85	$77.80
Purchase #4	$173.81	10.337%	$191.7767	$191.78	$191.80	$191.80
Purchase #5	$198.90	12.324%	$223.4124	$223.41	$223.40	$223.40
Purchase #6	$79.77	10.588%	$88.216	$88.22	$88.20	$88.20
Purchase #7	$115.92	9.592%	$127.039	$127.04	$127.05	$127.00
7 purchase totals =	$846.80		$933.6115	$933.61	$933.65	$933.50