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	$175.96	8.159%	$190.3166	$190.32	$190.30	$190.30
Purchase #2	$204.61	8.150%	$221.2857	$221.29	$221.30	$221.30
Purchase #3	$237.87	3.224%	$245.5389	$245.54	$245.55	$245.50
Purchase #4	$38.61	13.639%	$43.876	$43.88	$43.90	$43.90
Purchase #5	$189.60	11.253%	$210.9357	$210.94	$210.95	$210.90
Purchase #6	$184.88	6.267%	$196.4664	$196.47	$196.45	$196.50
Purchase #7	$6.87	6.511%	$7.3173	$7.32	$7.30	$7.30
7 purchase totals =	$1,038.40		$1,115.7366	$1,115.76	$1,115.75	$1,115.70