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	$155.31	12.116%	$174.1274	$174.13	$174.15	$174.10
Purchase #2	$177.90	3.438%	$184.0162	$184.02	$184.00	$184.00
Purchase #3	$242.71	13.296%	$274.9807	$274.98	$275.00	$275.00
Purchase #4	$184.95	3.431%	$191.2956	$191.30	$191.30	$191.30
Purchase #5	$80.38	11.227%	$89.4043	$89.40	$89.40	$89.40
Purchase #6	$200.50	6.356%	$213.2438	$213.24	$213.25	$213.20
Purchase #7	$48.40	9.248%	$52.876	$52.88	$52.90	$52.90
7 purchase totals =	$1,090.15		$1,179.9440	$1,179.95	$1,180.00	$1,179.90