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	$171.76	13.408%	$194.7896	$194.79	$194.80	$194.80
Purchase #2	$224.39	11.470%	$250.1275	$250.13	$250.15	$250.10
Purchase #3	$245.45	5.150%	$258.0907	$258.09	$258.10	$258.10
Purchase #4	$61.64	3.794%	$63.9786	$63.98	$64.00	$64.00
Purchase #5	$99.93	11.811%	$111.7327	$111.73	$111.75	$111.70
Purchase #6	$22.57	13.459%	$25.6077	$25.61	$25.60	$25.60
Purchase #7	$102.55	13.461%	$116.3543	$116.35	$116.35	$116.40
7 purchase totals =	$928.29		$1,020.6811	$1,020.68	$1,020.75	$1,020.70