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	$170.57	8.681%	$185.3772	$185.38	$185.40	$185.40
Purchase #2	$200.71	4.618%	$209.9788	$209.98	$210.00	$210.00
Purchase #3	$166.82	3.423%	$172.5302	$172.53	$172.55	$172.50
Purchase #4	$209.75	5.372%	$221.0178	$221.02	$221.00	$221.00
Purchase #5	$163.71	11.706%	$182.8739	$182.87	$182.85	$182.90
Purchase #6	$89.30	10.828%	$98.9694	$98.97	$98.95	$99.00
Purchase #7	$229.76	11.722%	$256.6925	$256.69	$256.70	$256.70
7 purchase totals =	$1,230.62		$1,327.4398	$1,327.44	$1,327.45	$1,327.50