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	$141.72	4.458%	$148.0379	$148.04	$148.05	$148.00
Purchase #2	$191.30	10.175%	$210.7648	$210.76	$210.75	$210.80
Purchase #3	$84.84	6.584%	$90.4259	$90.43	$90.45	$90.40
Purchase #4	$165.80	11.709%	$185.2135	$185.21	$185.20	$185.20
Purchase #5	$217.74	10.672%	$240.9772	$240.98	$241.00	$241.00
Purchase #6	$6.70	8.135%	$7.245	$7.25	$7.25	$7.20
Purchase #7	$194.69	3.119%	$200.7624	$200.76	$200.75	$200.80
7 purchase totals =	$1,002.79		$1,083.4267	$1,083.43	$1,083.45	$1,083.40