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	$35.71	5.277%	$37.5944	$37.59	$37.60	$37.60
Purchase #2	$237.42	13.655%	$269.8397	$269.84	$269.85	$269.80
Purchase #3	$158.35	7.834%	$170.7551	$170.76	$170.75	$170.80
Purchase #4	$19.79	9.807%	$21.7308	$21.73	$21.75	$21.70
Purchase #5	$181.68	13.645%	$206.4702	$206.47	$206.45	$206.50
Purchase #6	$241.30	5.575%	$254.7525	$254.75	$254.75	$254.80
Purchase #7	$50.47	9.179%	$55.1026	$55.10	$55.10	$55.10
7 purchase totals =	$924.72		$1,016.2453	$1,016.24	$1,016.25	$1,016.30