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	$189.38	3.717%	$196.4193	$196.42	$196.40	$196.40
Purchase #2	$32.58	9.216%	$35.5826	$35.58	$35.60	$35.60
Purchase #3	$105.32	6.827%	$112.5102	$112.51	$112.50	$112.50
Purchase #4	$79.25	6.763%	$84.6097	$84.61	$84.60	$84.60
Purchase #5	$172.67	7.175%	$185.0591	$185.06	$185.05	$185.10
Purchase #6	$222.33	10.228%	$245.0699	$245.07	$245.05	$245.10
Purchase #7	$195.75	7.640%	$210.7053	$210.71	$210.70	$210.70
7 purchase totals =	$997.28		$1,069.9561	$1,069.96	$1,069.90	$1,070.00