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	$77.66	6.352%	$82.593	$82.59	$82.60	$82.60
Purchase #2	$66.95	6.263%	$71.1431	$71.14	$71.15	$71.10
Purchase #3	$124.59	5.407%	$131.3266	$131.33	$131.35	$131.30
Purchase #4	$52.25	3.464%	$54.0599	$54.06	$54.05	$54.10
Purchase #5	$135.71	9.642%	$148.7952	$148.80	$148.80	$148.80
Purchase #6	$226.57	9.767%	$248.6991	$248.70	$248.70	$248.70
Purchase #7	$62.30	5.752%	$65.8835	$65.88	$65.90	$65.90
7 purchase totals =	$746.03		$802.5004	$802.50	$802.55	$802.50