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	$55.39	12.765%	$62.4605	$62.46	$62.45	$62.50
Purchase #2	$99.31	9.545%	$108.7891	$108.79	$108.80	$108.80
Purchase #3	$26.52	3.282%	$27.3904	$27.39	$27.40	$27.40
Purchase #4	$171.27	7.399%	$183.9423	$183.94	$183.95	$183.90
Purchase #5	$74.32	8.439%	$80.5919	$80.59	$80.60	$80.60
Purchase #6	$246.75	6.540%	$262.8875	$262.89	$262.90	$262.90
Purchase #7	$57.99	3.150%	$59.8167	$59.82	$59.80	$59.80
7 purchase totals =	$731.55		$785.8784	$785.88	$785.90	$785.90