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	$54.86	9.398%	$60.0157	$60.02	$60.00	$60.00
Purchase #2	$171.77	4.389%	$179.309	$179.31	$179.30	$179.30
Purchase #3	$208.63	7.255%	$223.7661	$223.77	$223.75	$223.80
Purchase #4	$228.50	11.690%	$255.2117	$255.21	$255.20	$255.20
Purchase #5	$225.37	11.118%	$250.4266	$250.43	$250.45	$250.40
Purchase #6	$91.86	12.273%	$103.134	$103.13	$103.15	$103.10
Purchase #7	$102.54	11.221%	$114.046	$114.05	$114.05	$114.00
7 purchase totals =	$1,083.53		$1,185.9091	$1,185.92	$1,185.90	$1,185.80