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	$156.97	9.308%	$171.5808	$171.58	$171.60	$171.60
Purchase #2	$93.26	13.325%	$105.6869	$105.69	$105.70	$105.70
Purchase #3	$117.33	11.741%	$131.1057	$131.11	$131.10	$131.10
Purchase #4	$148.56	4.754%	$155.6225	$155.62	$155.60	$155.60
Purchase #5	$32.84	6.730%	$35.0501	$35.05	$35.05	$35.10
Purchase #6	$189.30	13.721%	$215.2739	$215.27	$215.25	$215.30
Purchase #7	$191.78	4.606%	$200.6134	$200.61	$200.60	$200.60
7 purchase totals =	$930.04		$1,014.9333	$1,014.93	$1,014.90	$1,015.00