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	$80.83	10.403%	$89.2387	$89.24	$89.25	$89.20
Purchase #2	$7.94	7.513%	$8.5365	$8.54	$8.55	$8.50
Purchase #3	$186.96	12.685%	$210.6759	$210.68	$210.70	$210.70
Purchase #4	$125.43	12.113%	$140.6233	$140.62	$140.60	$140.60
Purchase #5	$212.94	11.826%	$238.1223	$238.12	$238.10	$238.10
Purchase #6	$51.54	9.736%	$56.5579	$56.56	$56.55	$56.60
Purchase #7	$215.31	3.632%	$223.1301	$223.13	$223.15	$223.10
7 purchase totals =	$880.95		$966.8847	$966.89	$966.90	$966.80