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	$164.39	8.292%	$178.0212	$178.02	$178.00	$178.00
Purchase #2	$119.67	6.127%	$127.0022	$127.00	$127.00	$127.00
Purchase #3	$183.78	5.868%	$194.5642	$194.56	$194.55	$194.60
Purchase #4	$211.62	8.428%	$229.4553	$229.46	$229.45	$229.50
Purchase #5	$12.54	10.712%	$13.8833	$13.88	$13.90	$13.90
Purchase #6	$140.67	10.545%	$155.5037	$155.50	$155.50	$155.50
Purchase #7	$127.39	11.681%	$142.2704	$142.27	$142.25	$142.30
7 purchase totals =	$960.06		$1,040.7003	$1,040.69	$1,040.65	$1,040.80