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	$122.46	4.328%	$127.7601	$127.76	$127.75	$127.80
Purchase #2	$166.86	9.586%	$182.8552	$182.86	$182.85	$182.90
Purchase #3	$65.98	11.772%	$73.7472	$73.75	$73.75	$73.70
Purchase #4	$62.37	6.196%	$66.2344	$66.23	$66.25	$66.20
Purchase #5	$200.61	11.480%	$223.64	$223.64	$223.65	$223.60
Purchase #6	$190.84	9.336%	$208.6568	$208.66	$208.65	$208.70
Purchase #7	$200.96	7.397%	$215.825	$215.83	$215.85	$215.80
7 purchase totals =	$1,010.08		$1,098.7187	$1,098.73	$1,098.75	$1,098.70